Instruct: Classify Amazon reviews into positive or negative sentiment
Query: value and longievity

I don't understand how this product is crapping out so soon for some reviewers. I just bought my second 501, and it's only because after SEVEN YEARS running the first one, I forgot to tell the pet sitter to replace the evaporated water in my reptile's pool. It must have been running without water for days! When I got home, the motor was still hot but it had stopped running. I wasn't able to revive it.This filter is fairly cheap, dependable, and whisper quiet. It may take a bit of leaving it tilted to get the "shooojsh" out until it's fully primed. Then it's practically silent. The only thing I wish they'd change is to make the top easier to remove. I have to use a lot of force- but at least I know it will never leak!I have a large lizard and use this filter in an about 5-8 gallon pool. I need to change/rinse media and clean the pool maybe once every other month. It's difficult for lizard owners to figure out what to use so I'm including this information.