Seems like there's still room for calyxes to plump more, but some plants have 'longer' hairs than others. (technically, hairs don't get shorter.. calyx plumps around them.. they do coil up when they turn color and die - pistil death isn't a concern and supposed to happen as it ripens).
Assessing trichome color is probably the best way to do it, but not all plants amber up. If you ever get that feeling that the calyxes are fully plump and it's been 7-10 days beyond that point... probably good to harvest those plants regarldess of amber seen.
the proflowers are the oldest and first to deteriorate.. if they turn color and are hollow/crispy, that's a potential sign of over-ripening, in my experience. Those 'preflower' calyxes are 1-2 weeks older than any of theothers, give or take. (the calyxes that form at each branch, initially, are preflowers ... not initial bud sites)