There indicas? or trimmed back sativas? If there in, i say it'll take about 8-10 before the chop, get a scope and peep the tricombs, look at them until most of them are milky then chop em down. too much red/amber, or clear, is a no go. the sativas take a bit longer, i think most of those run about 10-14 weeks. unfortunately, all my plants are sativas, so its extra effing long for my first grow...
When you harvest, dont just take the nugs, youll have tons of leaves and trimmings minus stems youll be able to make shake or keef with. If you go with the keef direction, youll have to buy something to sift all that shit, they make commercial buckets with layers of netting that basically does the work for you.