You can feed more for sure. I feed my 1-3 month old Panther Chams about 10-12 medium Phoenix worms a day each, in addition to crickets and fruitflies.
As far as how long they store. Depends on what stage they are at. Some places sell "small, medium, large".. Obviously the larger ones will turn to flies faster then the smaller ones, i've had small last for up to a month in a cool spot.. But you can also feed the flies, its great for active hunting.
PS: careful with the bedding, most places used some sort of sawdust. I've always been concerned with the possible impaction risk.