NIE expiry date (Valencia)

Hi there, i am moving to Valencia next week. I used to live in a town in northern Spain back in Protected content I obtained a NIE. I still have this scrappy A4 letter from the police with my official number on. However, I see no expiration date on it. Does anyone know if I will be able to use this when I return next week? I don't want to have to apply for a new one if I don't need to. Thanks!