How long does it take to bounce back/recover from antibiotic resistance- in particular, from prolonged use of anti-acne topical antibiotics?
I'm not sure how long it would take, since some people have colonies of antibiotic resistant bacteria even when they haven't been taking topical antibiotics at all. However, antibiotic resistance is more common in people who apply topical antibiotics intermittently or who often forget to apply the second daily dose. If you have been using Clindamycin, perhaps you could switch to Erythromycin or vice-versa?
An oral antibotic, Minocin, worked very well on my acne that I got when I stopped taking birth control pills and I only had to take it once a day.