Ya, the top couple inches always dry fast, but if you were to get water saturation tester, like $10 at any grow shop. And stuck it down in the soil it would read that it has plenty.
I would buy one, it's cheap and helps a lot.
I'm at week 4 1/2 and here what my babies look like.
So i think you have about 5 weeks or so, give or take a few. It's to have a specific day cuz all plants finish at different time. You just gotta read ur plant they will tell you when they are done. Cheers!!