Here's what happened to me:
Month 1: Nothing
Month 2: Slight improvement on the crown
Month 3: Considerable improvement on the crown, could no longer see through the hair while facing a mirror. Can still see thin areas with a mirror to look at the back of my head.
Month 4-7: Slow but steady improvement.
Month 8: Believe it or not, minor shed. I noticed no increase in fallout, but certainly I lost some results.
Month 9: Recovery. Areas that had "shed" regrowing.
Month 10: Like a bolt from the blue, hair line movement. Considerable change, while it's not perfect, the hairline is much closer to being square.
Month 11: Crown almost fully filled in now. Month 11 is technically August 1 for me, but whatever, close enough.
I've been on Accutane as well since Month 8.