I do it depending on the size of the animal and how strong of a hunter they are. If the animal is big and the smaller cage is looking small for it, or the animal is climbing all over the place (when your husbandry is spot on and you have enough pathways/vines/branches) then I move them. If the animal is smaller but I want to move it up as soon as I can, then I base my choice off of how good of a hunter it is. If it is active and hunts down the food with gusto (and has no other issues) I move it to the bigger cage. If it doesnt really chase down the feeders but kind of just waits for them to come close, then I wont move it until it is bigger/hunts more actively.