3 weeks or so.
If you wait until you have 98-99% brown pistils, this will put you in the "10-30% amber trichome" zone without having to look too closely and will also be the time for peak THC levels/potency.
@idkman1337 Hi mate I would actually predict slightly longer than the others have said
a minimum of 4 weeks more likely 5 by the time the calyxes have properly swollen
I know its hard to wait an extra week or two but the results will be worth it mate