the pistils will come and go and you may even get new one right up till near harvest. Every new one is basically a new bud forming. One they get about 6-7 weeks flowering it’s time to look at the trichomes. You’ll need a jewelers loupe or a really good magnifier
here is a pic of my gold leaf. She is right at 8 weeks now!
Thats a bud about the size of a beer can. I’ve got about 15 of them LOL