I have to admit that after we got our fridge, I didn't change the filter for almost 3 years. When I finally remembered it and changed it, I was actually surprised that it didn't look so bad. I know, I know, that's WAY to long and I'm lucky not to have had an overflow or moldy stuff in my water. I'm just relieved it wasn't as bad as I thought it would be. I do change it now every 6 months.