In Boxing today Fighters seem to be hitting there prime

[Cotto16]

early to mid 30's, 25 years ago that was old for a fighter, now it seems most fighters are hitting there best form round that time

The fighters below are all world champions and are looking better than ever and all are 30+
Manny Pacquiao 31
Sergio Martinez 35
Wladmir Klitschko 34
Carl Froch 33
Juan Manuel Marquez 37
Fernando Montiel 31
Lucian Bute 31
Danny Green 37
Serhiy Dzinziruk 34

[Adamj1987]

there also having less and less fights before title shots

[banjo]

Fighters generally fight less these days as well so there is less wear and tear on their bodies thus prolonging their careers, gone are the days when top fighters would have over 100 fights in their careers and bouts per year hitting double figures.

[stujones]

Agree Cotto, although being pedantic about your examples - Danny Green hasn't exactly fought stellar opposition of late to compare of him in his late 20's. Similarly, Dzinderuk.... well he just doesn't seem to fight.

[hurlock]

steroids

[glens73]

It's their not there

[jamesmcdonnell]

there also having less and less fights before title shots

Yes I agree, this is a major factor. Also, they have better nutrition, access to better medical care, and once they hit the top, fight 4 times a year max.

Factor in that they are probably a lot better fed than they would have been 20 years ago as children, and it's no wonder.

You've got the same top 10% genetics with 150% better everything else. No wonder.