PVP Ages last for as long as KI wants them to last. The first one lasted a very long time and the 2nd one was very very short. We are now in the 3rd Age. Your rating will be set back to 500 (Private) and everyone will start out at Private when they change the to the New Age. They didn't say that they were going to change in the Update Notes this time round, so I very much doubt that they will.