First time grower- need input on length of grow cycle, and maturity of plants

got 12 kids, maybe 6 or 7 are females, from seed till now is about 8wks, use a Virtual Sun grow-light(600w MH) with a 6in blower+scrubber/filter unit...FoxFarm Ocean Forest soil with Big bloom,grow big, and tiger bloom nutes, Ph is about 7, on a 18/6 light schedule, water 2x/wk feed every other watering. Plants are approaching 3ft tall, should I keep them growing to see if the other plants turn female?, each plant has been pinched 3 to 4 times, Don't want to rush anything but I am looking for as quick a turnout as possible, could let em grow 6ft tall but id like to experiment with 3-4 ft plants.......would like to post pics but don't think im allowed????

They will stretch some after you force them to flower so now is probably a good time to do it. If they are to tall the light won't get to the lower part of the plant. Wide is better than tall..........