I found out about these litterboxes by going into a pet store for cat supplies when I adopted my cat back in 2005. I liked the idea that I no longer would have to worry about having to scoop out cat waste or have a strong cat waste smell in my home.  I bought the LM920 which I found to have a quiet and decent motor. Unfortunately, it only lasted about three years.  Then I bought the LM900 as the LM920 was no longer made even though it is superior to the LM900 and quieter.  The first LM900 I bought lasted about a year and half, and I found the motor noisy and not very sturdy.  The second LM900 lasted about a year.  I bought the third LM900 and it only lasted two days before the rake stopped in the dumping into the receptacle mode and wouldn't move anymore.  I had to unscrew the rake so I could empty the receptacle which was full of lovely cat waste, dump the current amount of cat litter and return it to Amazon so I could get a replacement.  The replacement one broke also with the rake in the upright position so again, I had to unscrew the rake to get to the almost full receptacle to dump it out. Don't bother buying the Littermaid LM900 model as it is obviously doesn't last.  I went and bought the latest version of the Littermaid which is a LME9000 and it is better with a timer so the rake doesn't run during during a 9 hour duration but I still run into the rake getting stuck at various times and it also pushes unused litter into the receptacle.  I go through way more litter now which is frustrating but it does seem to have a stronger motor.