The pellets do not have to be changed weekly though correct? I though I read a post by @bpatters that said something like 6 or 8 weeks? I could be wrong though. My memory is not all that great lol.
I have not changed mine. My friend changes them every 8 weeks. It will depend on how much you put in the cage so when you stir it around there are still pellets to mix with the saw dust. I used one bag for a 2x4 cage and I will probably use 1.5 bags next time (40lbs), the bags are only $5 (CAD).