To be honest, it depends upon the type you buy. There are various types of air-stones/air-curtains and can be made from very different things. Some of the air-curtains that bend and have a rubber finish to them, will need cleaning and a bit of a stretch after a few months or so, otherwise it appears as if the air is becoming restricted. I have used air-curtains made from the stone type material and this seems to last a long time, I have had mine for a couple of years now without issue, but I do push around 4000ltrs of air out an hour, which is a lot.