Ive been playing guitar for over 15 years but seriously playing (i.e playing in bands) for around about 6-7 years but I recently stopped playing for 2 years and started again about 6 months ago. After 2 years of not playing it only took about 1 week to get good calluses back, and regain my finger strength/dexterity back to what I used to have. The good thing is that I dropped all my bad habits ive had since I started playing; like sloppy picking, and poor or no practice sessions. Now I practice everyday with a metronome and finger excersizes/scales/modes instead of just noodling around. My playing has improved 100 percent as a result and I guess my point is that the best thing for my playing was to quit for a couple of years.