The talk about PRIME is very big in classical boxing, fighters have different primes and rarely do they encompass all at the same time physical stamina & speed prime a physical strength/power prime A skill prime (usually later in their careers) A tactical prime Lets take some examples: Lennox Lewis: Physcial Prime: 1993-1995 (had much more speed/fluidity) Skill/tactical prime: 1998 onwards Duran: Physical Prime: Dejesus 3-Leonard Skill/Tactical Prime: Leonard-Hagler & possibly had his peak skill (not physically but skill) against Barkley Barrera: Physical Prime: Mkkinney-Morales or Hamed Skill/Tactical Prime: Hamed onwards Some things we can take from this: 1. When an old great meets a young physically prime challenger, although the youngster has the stamina/speed advantage the old timer may have skill/defense/tricks advantages. 2. In mythical match ups you can't take stamina and skills from different aspects of a fighters career. At lightweight for example Duran was no where near the defensive master he was at Welter-Middle
We also have to keep in mind that fighters fight to the level of their opponents. To use George Foreman as an example, well he looked fabulous mashing Frazier and Norton, but not quite as good against Chuvalo.
They also seem to have chin primes as well. Their chins are usually very good when they are in their 40's, look at Foreman and Holmes. They took some of Holyfield's hardest shots smack on the jaw and didn't move an inch. Fighters all age differently, look at the prime ages of Tyson and guys like Marciano and Holmes. They all differ.
I think the chins may have something to do with the mental makeup. Foreman was alot mentally stronger when he came back. Holmes chin never seemed bad to me in his prime he got dropped by Shavers big whoop and KOed by Tyson when he hadnt fought in like 2 years.
Chin also comes with balance and focus. Foreman was a very stationary fighter in his comeback. His main problem in the Lyle brawl was that he kept moving into Lyle's big shots. Holmes, in addition to being a more stationary target, didn't half-ass very much in his comeback...so it was alot harder to "Snipes" him. I think he trained alot harder too, so he was always pretty focused.
I dunno if I'd call the latter stages of success a prime. I think GREAT fighters have a prime..and then a rejuvenation/recreation period towards the end of their careers. If you wish to consider the latter portion a prime then I guess that's applicable.