My trays are changed everyday.

I only use a small amount of litter in each tray though.

My 18 year old cat doesn't go out much anymore so prefers to use the tray and my little girl cat has just had kittens so it housebound for the next few weeks.

If its a wee, I change it and wash it with hot water. If its just a poo then I can scoop which saves me chaging so much.