You can pay ahead up to 10 years, which helps. Get in the habit of adding time every year, but you can miss up to 9 in a row before there are any problems.
Kind of an odd example in this context? Someone who is incarcerated for that length of time is liable to lose any property they fully own anyway given the kinds of monetary damages that tend to go with it. And physical property isn't trivial to have kept up for a decade away from it in jail either is it? The only way that happens is if they have it legally isolated from them and someone else who can/will be a caretaker, and in that case said person could easily renew a domain as well. If anything domains would relatively speaking seem pretty easy there, no matter what jurisdiction you're under there are domains to be had that are under a different hostile jurisdiction, there are registrars that will accept cryptocurrency payments, and costs are relatively very low. Auto-renew from a private bitcoin wallet for $10-20/yr on the face of it looks more sustainable and feasible to have work and survive court judgements following a serious felony. And during trial there is time to prep.
Nothing is perfect and the domain situation is really far from perfect, and it doesn't hurt to consider edge cases. But the Venn diagram intersection there of someone who cares enough to have custom domain that is critical, commits a serious felony, considers having the domain after release a key priority, isn't legally barred from it, and doesn't or can't take any steps towards it, seems kinda small. In that case maybe indeed "domains aren't for you" but that doesn't really take away from its use to the rest of us.
I think you would get a confluence of many of these when looking at computer crimes, because often a condition of the sentence is being unable to use a computer (and, to some extent, a lot of people who spend time on computers lack physical people in their life who can step in to help out in situations like these…)