G.T.
Mine usually takes a few months before it starts to get weird... then I just buy a new one. I spray mine with a cleaner that has bleach in it, keeps it pretty good for a time. My husband is bad about not spreading it back out to dry properly after he has his bath in the morning, and sometimes I forget to do it myself. But if you spread it after showering and bathing and have some decent ventilation, it should be okay. They only get messed up if they stay wet.