I started it with my new kitten. He took to it which i was grateful. I am not willing to risk changing now - they may start to have issues with new litter, I just won't go there but... this is a very nice system. It helps a lot and I do like it. It does NOT however do anything even close to what they claim. It is better with odor as it moves it onto a closed off tray area but I still scoop it out later as it does (of course) still smell. What I don't like..... it is EXTREMELY expensive for what you get. I have never gone beyond 2 weeks and even that's a stretch - they whole thing just starts to smell again (of course ) it will. Most honestly I make it a week and some days. They claim to 3 weeks but this is ridiculous unless you don't mind the rancid smell - it does not last that long no way. So if you don't mind spending the money - the truth is you will get probably around 8-10 days.