In reply to mikeski:
Nah, still pretty much 50/50. Both do excellent work most of the time, but with the occasional disaster.
To the OP: typically about a week or so I think. I've taken quite a few pairs in, one pair were just never quite right again but it was money well spent for all the others. (And one pair of trainers were even better than new - the original soles weren't as good as the Stealth 'dotty' rubber soles they have now.