I love the top down litter box and these liners are non essential (you could always just put the litter directly in the box) but really do help. The last one lasted about a year before starting to look a bit ratty with three cats constantly using it, so it's pretty good value. When you want to clean the whole box properly you can just lift the litter out and put it in the bin, wipe the box, put in a new liner and litter and it's over.