I mean, at the least, can't you make it a deal that you're OK walking away from if you find yourself in this kind of situation?

Sure, you could sell the biz outright and wash your hands of the whole thing once the check clears.

I dream of that moment but can't help but feel I'd be doing something or someone wrong if I just disappeared to a small island somewhere expensive. Is it really possible to just disconnect after a sale? I'd be interested in hearing supporting anecdotes as well as to the contrary; I want to believe!

The company you sell to cannot legally bind you to working for them - that is indentured servitude. You can always leave any contract or job any time you want. The OP mentions "once the check clears" for good reason - because when making acquisitions your payout is usually contingent on staying around for the transition for a fixed amount of time - you don't get your payout until that deadline, and if you leave before then you void the obligation.

How practical is that? I guess more concretely, what kind of discount would you have to accept if you weren't willing to stay on for 2 years or whatever the standard practice is?