They could still be alive in your harvest for three to four weeks no joke.
That is true. Not the adults but eggs will be there and depending on temps can hatch weeks later.
I've had to harvest with active mites and it sux big time but something I read recently makes a lot of sense and I wish I'd seen it before my last mite-ridden harvest.
Chop the whole plant off at the base and hang it upside dow, F'n mites are always climbing to the highest point so make the base the highest point so they head up there to launch off to new territories.
I taped some window screen over the end of the crevice tool for my house vac and that did take all the webbing and bugs off the colas when I cropped. Mites don't dig down into the buds so a good trim and shake over a screen gets rid of everything really. If they are really everywhere they suck the life out of your plants and yields will suck too. Not to mention bag appeal. lol