use them for 22 years, they develop a fair amount of float ;-) I sometimes remark how worn they are and how much my feet move around, even when I got the new M520s, but for just regular riding its never an issue. I suspect if I stand and twist a lot they may release, but with regular riding they are still safe.
I assume the newer ones will be just as good over the long term re the bearings inside, I hope so anyway and going from 5 years of use, they seem to be just as good.

as with all bike maintenance, once in a while and after riding in rain I take a rag to clean out the recesses, and spray wd40 or whatever to clean out grit and stuff from the spring mechanisms, so Im sure this helps with them lasting a good long time. That said, the inner bearing setup must be a good design because other than surface wiping, and take care not to push grit inside when cleaning, I dont do anything to the innards.