lets put it this way
i have never cleaned my grinder, but i always clean my hands.
If im breaking up by hands im just washing away any trichs on there...
my grinder collects what would normally rub off onto the bottom.. and the walls/teeth collect keif over time... but walls and teeth will only collect so much until it starts falling off when it's added on...
so with my grinder im at the point where ANY amount of keif that sticks to the wall, will just result in other keif falling back onto my product. If keif STUCK permanently, and never fell back onto the screen/grinded bud... then I would have 4 inch keif walls protruding from the walls of my grinder
Also, I have a few vials full of keif from my keif compartment...from the last year or so of grinding.. i dont sift... and I dont notice any decrease in potency

we are talking very
very small amounts here people..