We had one about 11 year ago and our oldest cat (at the time)
urine made such a LARGE clump that the "rake" had a hard time
moving it. After about 5-6 months it broke.
If you have more than 1 cat I don't recommend getting it unless
you plan to get more than one box.
I think the main reason ours broke so soon was because we had
3 cats.
But it was great while it lasted.