(Spoilers Extended) Theory about the Long Night and the Bittersweet ending to the series

I have little proof for this but there is a possibility of it happening. We are told in the books that the Others invaded during the Long Night 8000 years ago and the next Night may come when they finally come south. My theory is that the Long Night is a magical event that occurs once every 8000 years and it will keep happening even after the end of the series. I think that whoever Azor Ahai is will only drive the Others back north like last time and they will go to sleep under the ice and wake up 8000 years later for the next Long Night. So the bittersweet ending that is apparently supposed to happen is that the Others will wake up again for the next Long Night and invade again.