G'day, a few things. Not all plants will develop amber trichomes, so waiting for plants that never get them can lead to harvesting over ripe plants with degraded THC and harvesting plants that are close to death. Secondly, by giving them weeks/months at 24/0, this may have caused problems, as plants need a dark period every 24 hours to complete their photosynthesis and this is why 18/6 is optimum. By not getting a dark period to be able to complete their photosynthetic cycle, this leads to plants with an incomplete metabolism, which may then lead to incomplete cannabinoid sythesis, possibly accounting for the lack of amber trichomes (maybe).
At this stage, if you have 95-98% brown pistils, you are well and truly in the zone for harvesting, much longer and/or waiting until all the pistils are brown and withered, actually leads to trichomes with reduced THC and elevated CBD and CBN levels, giving you flowers that produce a more sleepy/heavy body type of stone, rather than a mind bending head high of earlier picked flowers (90-95% brown pistils) with their peak THC content.
All of the signs you described in your question are signs of a plant that is close to death and probably past its prime, so I would suggest harvesting sooner rather than waiting another week, otherwise you could end up with buds that put you to sleep, but don't get you that bent.
I would also strongly advise you to go to 18/6 on your next crop, plants do need sleep and the myth that it is OK to grow auoflowers for their entire life with an incomplete photosynthetic cycle (24/0) and then still being able to produce top quality buds needs to removed from the world of cannabis cultivation. 24/0 could only be recommended by people who don't understand how plants function and/or don't understand photosynthesis. Besides, cannabis can only grow so much during any one 24 hour period and this growth tops out at around the 18 hour mark, meaning running your lights any longer than 18 hours is basically a waste of electricity.
So, I would suggest harvesting now, or very soon, and believe in your gut feeling that your plants are ready for harvesting.
Hope this helps, Organoman.