"All-Time" Favorite Album/Song

How long do you need to wait until an album or song is considered an "All-Time" favorite? A friend at work today said that his dad said that the new Eagles double album was his one of his "All-Time" favorites. Of course it came out just a little over a year ago. The son of course said that is a pet-peve of his. So then I asked, ok how long until it can be labeled "All-Time" status. He said 2-3 years. I've asked a few others and they range from 5, 10, 20 and even got a exact 7 years. For me...If it goes back to "Front to Back"...In 2 years, if I still love every song front to back then it becomes "All-Time" status after that 2 years have expired.