Have your players ever put a bounty of a BBEG after he escaped? I would imagine it would be quite theraputic. Instead of waiting for him to seek revenge for destroying his minions and taking his treasure, you put a bounty out there with your spoils and have him hounded by other adventuring groups, then you sweep in for the kill. Why be on edge of when he might attack you, keep him running for his life.
No, but I once had the BBEG teleport away right when the PCs were about to nail him... only for them to read in the next day's newspapers about the guy being found dead in his home (secondary poison damage kicked in after the teleport). We'll never forget that one.
My players ? lmaorotfl
No, sadly, my players have not been so imaginative as to actually DO that (although one of them, once, mentioned that as a theoretical possibility - until he realized just how broke his character was). I've done it ... overdid the bounty a tad and found someone analagous to Boba Fett's reputation bringing me a head in a basket tho. Ooops. Fortunately, I was smart enough to cough up the bounty money and have the head bronzed.
It IS an effective tactic with a reasonably fair GM - in d20 terms, be careful of supplying your BBEG with too many unplanned-for experience points, as he may gain enough xp that way to straight up stomp the group when next you met, " fair CR " be danged. That BBEG will be coming back for you as soon as he is able to track you down and butcher you. First clue might be from the deaths of all the people you pawned his unusable loot off onto. Or, the other hand, a clever group of players will arrange for something analagous to a bio-monitor (or simple scrying) on those who acknowledge acceptance of the bounty and watch what they do, find out what they find out ...
Possibilities for that are endless ...