This topic was covered quite recently. Most of my trays I have had for many years and are as good as new, not even scratch marks on the bottom. A lot I think depends on the type of litter used. A few weeks ago I was looking after someone's cat and they brought its own litter tray, thinking that I would not have enough. I personally would have been ashamed, as although very clean it has a layer of grey on the bottom, obviously some type of horrid litter has been used. I used one of my own but all week I soaked the tray in everything to try to remove the litter residue and scrubbed it until my hands were sore, all in vain. I am sure if the tray had been thoroughly cleaned every day it would not have been in that state.
