What color are the trichomes? No matter how long you want to push them or grow them the perfect time to harvest is only dictated by trichome color and by nothing but trichome color. Plant size, yield, bud color, pistil color yellowing leaves or any other sign of maturing or any given number of days or weeks for flowering provided by breeders are not accurate enough to harvest by and be able to harvest when your plants THC levels have peaked.
 
Also, regardless of what anyone tells you after looking at pictures of your plants keep in mind what they say is at very best a rough guesstimate and should not be taken as being accurate advice to follow. No one, and I mean NO ONE can look at a typical picture and say plants are ready for harvest or they need a couple more days or a week or two and that is precisely when you will want to harvest to get the most from your plants. It is utterly impossible for anyone to do that with any consistency of even being close to accurate.
 
If someone can post ultra clear very close up pictures of their plants trichomes, on all levels of their plants – top, middle and bottom - where there is enough clarity that the true trichome color(s) can be seen even then the very most they can tell you as to when to harvest will be based totally on their personal preference for more of a head high or more of a couch-lock body stone that would be achieved by harvesting when the trichome colors would best give their personal preference.
Even in doing that they likely would still not be all that accurate since growing conditions and genetic differences will always factor in to some degree or another and what might be completely accurate in their growing conditions and for the genetics they grow or grew those things will be at least slightly different and possibly greatly different thus negating all they said.
 
In a case like that, with ultra clear close up pictures, if they really want to help you they will teach you what to look for so you yourself can decide when is best to harvest so your plants will then give you what you most prefer and not what they most prefer, or possibly inaccurately believe to be best.