pre flower's are just a indication of the sex of the plant,its the time change that trigger flowering.
Just mean the plant is at its sexual maturity,but a plant can be kept in veg mode for years,i have females that i have had for well over a year.
With out the time change,be it the plant wanting to flower or not it will not flower with out the 12/12 off period.Unless like i said above it is a auto
You never go on the pre flowers these just indicate,its sex and maturity,normally showing,in 4 /8 week,normally the 4 th week.
Male pre flower's normally show at 6/8 week,in plant;s that are grown from seed,
The pre flower's emerge at the stipule,at the 4/5th branch,internode's and do not normally turn into,full flower's
hope the helps