On the subject of beating old fighters:

A prime Mike Tyson demolished a 38 year old Larry Holmes in 4 rds in 1988.
About a year-and-a-half earlier in 1986, Larry had fought the rematch with Spinks for the Title.

..and in 1992, 4 years after the Tyson fight, Larry went on to defeat a prime Merciless Ray Mercer, and also win quite a few rds against a prime Holyfield in their 12 rd Title fight. That should be considered...