Light schedule directly affects maturity. Plants should show faster under less hours of light. Your plants should have shown by now. Topping might slow them down but only a bit. When reducing daylight hours your lights will turn off at the same time but come on later and later.
Example:
24/0, Lights never off
20/4, Lights off at 12pm (noon), on at 4pm
18/6, Lights off at 12pm (noon), on at 6pm
16/8, Lights off at 12pm (noon), on at 8pm
14/10, Lights off at 12pm (noon), on at 10pm
12/12 Lights off at 12pm (noon), on at 12am (midnight)
Theoretically plants should show sex faster under 12/12 than 18/6, but only by a matter of 2-3 weeks. Same goes for 18/6 vs 24/0. Then again, you could be staring at a group of females and don't know it. Typically females take longer to sex than males. Males almost always show sex first in my experience.
M.