I think it's supposed to take about 5 weeks, maybe less if you are using hydro.

I'm scrogging too (soil tho) and had asked how tall the buds would grow from the screen to maturity - but maybe somebody will - uhm - shed some light - or venture some opinion or averages on this.

The answer for my the height question probably depends on the nutrients and species one uses... but 5 weeks of 12/12 is what I thought I read for a well established root system.