I suspect I'll have more to say about midcareer mobility in the coming years, but from chatting with some friends and colleagues over the past few weeks, it's clear that it's the fear of no future mobility, of a lack of options, that gets most of us--even if we're not looking; even if we're pretty happy where we are.
There are a lot of reasons for this, but one I've been chewing over is the legibility of a new job: in part because mobility is so constricted and jobs are so few, moving between tenure-track jobs is a visible sign of success. (Assuming, of course, that it isn't the result of a tenure denial.) And though no one can make it through graduate school and junior professordom without being internally motivated, our lives up through tenure still involve a lot of external validation.
Getting a job is a big deal. Getting tenure is a big deal. Getting a book published is a big deal. But after that the achievement curve starts to flatten out and there are fewer truly new things to do. As the saying goes, the reward for winning the pie-eating contest is more pie.
Now, I like pie--which is to say, I'm reasonably content with the thought of what lies ahead. I'm immersed in my next book project and looking forward to being able to play a bigger role in certain things at the departmental and college level. But if my career is a narrative, it's entering a pretty boring phase. It'll be years and years before my next book is done, and even when it is, it's not going to be as big of a deal as my first book. Not because it won't be better; I hope it will be better. But it's not going to be a public accomplishment in the same way, something that inspires a flood of congratulatory emails from high school and college friends, distant relatives, and people I sometimes hung out with in grad school.
So I think some of the anxiety about mid-career mobility is about what it would mean not to have much visible change for the rest of your life, and not to have any markers, legible to others, of how well you're doing. If you're already at a top school, well, maybe that's okay: your mom is proud that you teach at Stanford; your peers respect your first book; it's all good.*
But if you have even the least sense that your institutional affiliation doesn't quite signify to others what you're about, it may be a different story. None of us, wherever we teach, is going to get big public accolades for our research; if we're lucky, a few hundred people read what we write (and a few dozen know how to value it). But it's easy to fear, if you're at Middling State U., that even fewer people will pick up your work to begin with. Moreover, if Middling State doesn't particularly reward or recognize research, it may feel like no one knows or cares what you're up to. And at a certain career stage, a new job may feel like the only truly legible sign of success.
(Now sure: you can say that we should all be completely internally motivated; that no one does specialized research for fame and fortune; that even those at prestigious research institutions are speaking, primarily, to a handful of specialists outside their university walls. But it's undeniable that some institutions provide more recognition, and more material compensation, for research than others.)
Personally, I have it pretty good. I can probably do the kind of work I wish to do at either my current or future employer. But the long-term consequences for humanities research, faculty life satisfaction, and even institutional prestige are unclear in an era where virtually everyone teaching at the college level has been trained as a serious researcher but employment prospects and mobility are sharply limited.
One possibility is pure waste: all that work that could have been done doesn't get done, because the scholars who would have done it don't get jobs or don't get jobs that adequately support their research. Another is a radical reassessment of the academic hierarchy: if an increasing number of people making careers at 3/3 and 4/4 institutions (or as adjuncts or independent scholars) produce work that's just as good as that produced by some of their peers at R1s, do we reevaluate what it means to have a "research" job? A third possibility, I guess, is a bunch of frustrated and unhappy people.
Maybe things will become clearer as the next decade or two play themselves out in the life of the academy. But in the meanwhile, a lot of people will be dreaming about their next move.
*I mean, except for the work itself, which may still cause you plenty of anguish, self-doubt, etc. But that's to be expected.