I'm not sure how long it lasts but it's more than just through quick on/off cycles. Somewhere I know that I've seen them discuss it from when I was looking at buying but heck if I can find it now. If you give them a call I'm sure they can tell you. I have all of my tanks on UPS now so I don't see that very often unless it's off for an extended time and runs out the UPS. I know that I've had some that have which lasted for probably 6 hours or more beyond that and I've never had to do anything to the time/programming as far as I can remember.