He was considered old when he beat Felix Trinidad in 2001. 12 years ago. Let's take a quick look at his resume from 2001 onwards.
KO'd Trinidad
First man to stop DeLaHoya
(Two close fights with Taylor)
Tarver
Wright
(Close fight with Calzaghe)
Pavlik
Jones
Pascal twice (one win one draw)
Dawson twice (his first clear loss since the first Jones fight)
Cloud
And a bunch of solid B and C level guys too like
Ornelas, Allen, Eastman, Joppy, Daniels and others.
That's a better resume than most fighters of this generation.
And that's what, half his career? All whilst aged 36+
And if we look before then he has wins over guys like Glen Johnson, Echols, Holmes, Allen.
What a remarkable man. How long can he stay at this level? Will he still be around at 49? 50? Will anybody ever break this record?