well, my fastest strain to be flowered, and done,. was about 6 weeks from 12/12, i had some take 11 weeks from 1st flower, total of 13 weeks. it is all in strain/genetics you are working with.
all i can recommend, is when you think it is really done, pick a lower bud, slow dry it for 3 days, in closet, and try it, and ask yourself, is it really done, i bet it isnt. 1 week can almost double the length the stone lasts, trust me. by doing it this way, to choose a harvest date you gain 3 days from testing the cut piece, and then, if you choose not yet, wait 7 more days, try again, this will be 10 days from 1st cutting your last taste. repete if needed 1 more time. you want some of the THC to change into the other helper canabinoids, CBN/CBT i think they are. you have to mature the crystal a bit, waiting 1 week to 10 days more really can be a big differance.
you will see it when it matures, your buds will swell up, the calixs will go into like a false seed mode, and the calexs will get 3x to 5x bigger all at once, the buds will look like they took a big breath, and swelled up. and about 50% to 75% of the hairs will have changed color, or shriveled up into its calex.