The pistils will turn orange and curl in multiple times during the flowering stage, this is an old school “old wives tale” (for lack of a better description) and doesn’t give you an accurate timeframe of when to harvest.
You’re on the right track with the trichomes changing color.
Milky white = more heady
Amber = more body “couch lock”
Waiting on percentages of white to Amber trichomes depends on what kind of high you personally enjoy.
Prefer energetic buzzy weed? Harvest at Low percentage of Amber trichomes.
Prefer a stronger body high and more of a relaxed couch lock feel? Let those trichomes go amber.
The trick is not harvesting too early or the thc % will be quite low and you’ll get very little high from your weed which I can say from experience is quite the let down after the amount of time put in
However, waiting too long and the trichomes will start to degrade as well.
P.s 8 is the avg time for flowering, there’s plenty of strains that take a bit longer say up to 10 weeks, or less if it’s fast flowering.