We recommend replacing Flip paperboard liners when there are signs of wear and tear to keep bacteria and odor in check. The longevity of the liners depends on how much litter is used, how many cats use the litter box, and how ferociously they scratch. Daily scooping and sustaining the litter level at 2-3 inches (5-7.5 cm) will maximize the life of the liners.
That pretty much sums it up. Purchase never arrived.
Good alternative to plastic!
I was skeptical to try the new paper liners but they are good. One tip is to pay attention as to how saturated they become and not go as long as you would with the plastic liners otherwise it's a messier clean up. I was concerned the paper backing isn't as high as the litter box (my cat is a high pee-er) but it was fine.
I’ve had the Flip Top Cat Litter Box for 9 years and the cardboard liners work so well. So glad I can order them online as they are no longer available locally.