Soon the philosophy job market will be in full swing again. Where and when should you apply for jobs? Only to dream jobs or to anything that moves? Should you wait until your viva (doctoral defense) or can you already apply as an ABD (all but dissertation)?
I'll focus on the when and where to apply for jobs, focusing on tenure-track positions, and I'll start with the question of whether ABDs should apply for tenure track jobs.
Should you apply for tenure track jobs while ABD?
It seems like a no-brainer to me that you should, if you reasonably expect they can finish the dissertation before the job's starting date. I know a couple of people who didn't finish and lost the tenure-track job they got offered, which is obviously disastrous. But if you are confident you will finish in time, I don't see a reason not to apply.
There are several reasons to apply while ABD. For one thing, if nothing else, you get experience letter writing, and if things go very well, interviewing - valuable experience that you can use the next years. No amount of mock interviews gives you a sense of what an actual first-round or on campus interview feels like.
Also, although the chances for ABDs have gone down, you might still find a job that is a good fit in your final ABD year, and such an opportunity might not present itself next year. The job market is stochastic. You can have 28 jobs advertisements in your AOS one year, and only 9 the next year. So you need to take every chance you can get, since some people are still hired while ABD. Here's an experience of a friend of mine, who got his TT job at a small liberal arts college while still ABD. He had no publications (he has plenty now, in good places too, and is well on track to meet all the requirements for tenure), and his grad school was not in the Leiter top-25. But the hiring school was a good fit: the job they advertised was straight in his dissertation topic, and they were specifically looking for someone in that AOS. He applied to just a few places, and wrote a couple of well-tailored letters (see here on excellent advice on how to tailor your letter).
When you are ABD and on the market, you want to assuage any concerns they might have about you finishing. This task falls mostly on your advisor (and perhaps other letter writers). You should explicitly ask them to say something about the materials they've seen so they assure the search committee members that it's nearly complete.
Worries of staleness
Now the other end of the spectrum: you've been in temporary positions for several years and fear that your PhD is getting "stale". My impression (and Marcus' analysis) suggest that staleness issues aren't such a big concern as long as you publish and teach. That being said, there is still some bias in favor of the bright young person full of promise and unrealized potential. There is even empirical evidence showing that people place more value in unrealized rather than realized potential. Someone I know who as on a search committee for a TT job said "I was surprised at how strong the preference was for bright young people on which my fellow search committee members could project all their hopes and dreams".
Still, I regularly see people land permanent jobs in good places who were on the market for many years. Just very recently, friends of mine who got their PhDs in 2005 and 2008 landed permanent jobs (both outside of the US, so not tenure tracks, but equivalent). You can put your experience to your advantage if you have a solid record of published research and teaching evaluations. Regardless, there is only one thing you can do, that is under your control if you want a job, and that is to apply.
How wide to cast the net
Where to apply to? Some people cast a very wide net and apply to 50 or more positions per year (or something in that order). Their reasoning is that the job market is a lottery, and you need to buy as many tickets as you can. But if they tailor their letter, that would seem a gargantuan task. You really need to tailor your letter (an easy and straightforward way to do this is to have a separate paragraph "At school X I would look forward to…") Still, even with one tailoring paragraph per letter, the time you need to spend researching department websites and people you could collaborate with adds up quickly.
So, as a rough guide: if the AOS they list is not among your AOS, it's probably a waste of time applying. Lack of fit is an easy way to make a first cut for search committees. This also means you need to consider carefully about what your AOS are. If you have significant postdoctoral experience and you've published in an area outside of your PhD topic, you can list it as an AOS (although take care not to over-list AOS, even if you have wide interests - it does not look convincing, as Alex Gelfert writes).
Do not make your search too narrow
On the other hand, it seems a bad idea to apply only to jobs that are "perfect fits", where also the desirable criteria or the AOCs match yours perfectly. Karen Kelsky (I can't find the source anymore), job market consultant, says that in her long experience of coaching job candidates, perfect fit jobs rarely come through, whereas "stretch jobs" (jobs you might plausibly fit in, but that aren't perfect fit) regularly do. She does not know whether this is because search committees are inscrutable to candidates, or because people want the job so bad they end up sabotaging themselves.
It is therefore recommendable, psychologically, not to ever let yourself believe you are the perfect candidate for job X, you've got no way of knowing that. Twice I had the experience of getting to the interview stage, but not being offered, a dream job (wonderful location, wonderful department, etc) that I believed was a perfect fit. And in one instance, the feedback I got was that the person who got it was a better fit. You can imagine how crushing an experience that is - I looked up his CV and I (obviously!) thought he was a far less good fit than I was! But then, as a candidate you have so little information about what a department wants, you cannot use your expectations and self-assessment to form a reliable view about how you fit.
Should geography and prestige of school guide your decisions?
Even in a buyer's market like this, considerations such as geographical location and prestige of the school play a role for people to apply to positions. I've often thought job so-or-so was a good fit for someone I knew, let them know about the job, and find out later they did not apply. They would say things like "I could not imagine myself living in XX" or "That's a 4/4 teaching load, much too heavy to my taste", or "The fact they don't speak English in country XX is too big of a barrier for me to move there".
Now, there might be serious reasons for you to restrict your search geographically. The two-body problem plagues a lot of academics, and spousal hires seem to have become very rare (except if you are a super-star in which case you're probably not reading this post). Some people are bound to a location they cannot move from, having commitments such as care for young children and a partner who cannot or will not move. Disability, caring commitments etc may prevent people from widely applying.
Still, if you can, apply widely even to areas that sound unattractive to live in. If you haven't lived there, you don't know what it's like to live there - it's as L.A. Paul calls it, a transformative experience, at least in an epistemic sense (and also in a personal sense), to move to a new location. You might be pleasantly surprised. Also apply to jobs that are not prestigious or have high teaching loads. Those are the majority of jobs after all, and you might still like doing them even if a teaching job is not what you first envisioned. Do consider Europe. European jobs have excellent benefits such as paid holidays and maternity leave, paid sick leave, and the pay might be on average lower than in the US, but you often have better provisions (such as cheaper healthcare or childcare) to balance that. Read my post on the European job market to learn how to apply.
The only situation I see not to apply to anything that is a plausible fit (barring any personal circumstances etc), is if you are in a cushy multi-year postdoc position with plenty of research time, which would allow you to strengthen your file considerably before going on the market. You'd be able if all goes well (and not everyone manages to optimize their postdoc time!) to get a much better position with that experience under your belt than if you accepted something right out of grad school. Probably, but with the state of the market it's not a sure thing.
In this situation I'd recommend: apply rather selectively in the beginning, and to anything that moves when your contract is nearing its end. Even so, don't apply too selectively because being early in a postdoc means you'll have an alternative option to walk away if you don't like the starting salary or other conditions, and such things are crucial in negotiations (I am planning to cover negotiation later in the boot camp). At the end of a job, your negotiation position is considerably weaker except if you have a competing offer.