Depends on how messy they get. I wipe them down with a damp cloth every week when I clean the cage, but I usually only haul everything out and do a full scrub every 4-6 weeks or so. Crash is litter pan trained, so he doesn't pee on his shelves. When I lived with my ex and his chin, though, we did the shelves every 2 weeks b/c Cervantes did a lot of territorial scent marking. With yours being female, I'd take a stab at once a month being sufficient for a hard scrub, unless she sprays a lot.