What about the equatorial strains developed in countries on perpetual 12 hour days...do these not flower based upon age?.
in the equator they can only veg pure(or close to) sativas, indicas will go straight into flower anytime of the year.
That's why it takes so long for pure sativas to start heading in non equatorial places.
In NZ at 37.4S indicas will have started flower by end of January, pure sativas can take as long as mid-late march before the even begin flowering.
If you're strain hasn't begun flower by march it's safe to say it's 85% sativa minimum.
My daylight hours are 12:30 at the moment so my equatorial plants(Malawi) should start flower in the next few days if not already.