I have grown many autos and found that all took a minimum of 80 days from sprout to finish with several going close to 100 so you are weeks away if you "seem to be" on day 56. Just note the sprout date and as you approach day 80 from that date, start watching for the same signs that they are ready that you would see with photos - all pistils orange to brown and receded into to plump calyxes. Also - and this just may be my environment - I find that most fan leaves are yellow or beginning to yellow. Personally I don't bother checking trichomes.