My own thinking on this subject is in constant flux.  Thanks for everyone's input, and I hope more take a look and don't be bashful about changing your mind.

To simplify my position (pretty complicated in my head), I'll say that as soon as FSS-RBF or CPFP is a common solution to having failed to pay a high enough fee, I think I might switch my answer to "Let them stay full until a better solution is found."  I might switch to that answer sooner, but it sucks to be in limbo because you didn't change your (cheapskate) wallet's default fee.