How often should I change the aspen bedding?

I use aspen in my BP cage, and it sort of smells bad and it's only been in for about a month. There's no poop and I think the smell is just the aspen, but how often should I change it?

I completely clean out my tubs monthly. I personally use those bleach wipes to clean out the inside, then rinse out with water and towel dry and place all new bedding in there. I spot clean the tub in between cleanings.

i spot clean everyday, and clean out all the tubs at least once a month.

Once a month like others have stated

spot cleaning when needed with my aspen, just take out the soiled area and take a handful of new and fill it back in.

monthly I usually just clean all of if out.

Yeah I do monthly too but I just switched back to repticbark cos I hate how the aspen clumps all together and I just find it hard to spot clean specially with the turds my guy's been dropping these days