For playtime fun, I change any wet fleece pads daily. The bigger pads just get a brush/shake and keep going unless wet or I decide it’s wash time. Sometimes a week, sometimes I stretch to 2 weeks.
Ultimately depends on how long the boys have used the playpen. At this time of year it’s a couple of hours every evening. In the heat of the summer they live on the floor & I treat the playpen the same as normal cage cleaning.