I top the plant suntil i got a good amount of tops, and i do it until 1 weeks after switching to flower......It really depends in the plant how often i do it. i start topping then 3-4 times then i do supercropping and if the plant grows nicely i top again, and after that aagain supercropping. I do it until 1 week before flowers appear, or easier said i stop if preflowers show up, maybe a few dys longer