Oh I guess I could post (I initially read the post as just being reptibark), since I currently use aspen or the expandable stuff for my bp. I spot clean for roughly a month, and then I dump it all and scrub down everything. If there are places where it looks like it's staying really damp (like underneath the water dishes) I either mix that stuff around with the other dry areas of his substrate, or I replace those sections after 2 weeks.