 They're probably fine at six months, but if you really want to make sure they're going to last a long time, every three and run it until it's hot. So fire it up. I don't know if you've got a clutch where you can engage the pump and leave it off so you're not running it dry. You might have to put some water in it, and then you've got to drain it for freeze protection. But if it's a pump you can run...