when you think they are completely finished,80 to 90 percent of hairs are receeded than add 1 more week and there done.When you got a ton of white hairs still growing its not even close.Also the tops will finish always before the bottoms so i normally give the bottoms an extra week after i cut all the tops.Hard to tell how much bigger they will get after a week or two freshly cut but when you compare them after they are dried the ones you gave an extra week will be noticeably fatter.
I would wait till week 9 but that's me. After week 7 switch to just water and molasses and by week 7 just water till week 9. Then whatever you do after that. I personally put my plants in a tent in the dark at 30%rh for 3 days. Helps the metabolism and finishes her out