Deep dig box

Hey recently I've been seeing really deep dig boxes for in the cage, right now my rats only have 4 inches of bedding, but the deep dig box seems like a good idea. My only concern is how often do you have to change it out considering it is considerably more bedding. Because if it's weekly like usual that seems like a lot of money to go through. And also any good bedding U.S brands? I've switched to Aspen recently by recommendation and seems to be good with the Rats but haven't been able to find any cost friendly brands. Thanks 👍