Can Floyd fight in his 40's like B-hop?

Yes, and I believe we'll be seeing a lot more of these skilled fighters successfully fighting into their 40's like JMM and Hopkins.

Could he? Yes, he keeps himself in xlnt shape.. Would he remain undefeated? I don't think so. Do I think Floyd wants to? Not at all. Do I think he will? No.

Mayweather was born and bred to be a fighter. So yes he has the mental makeup, style and skill to fight until 40 if he wanted to.

Discuss.:boxing: Yes he can but he won't because he wants to retire undefeated.

Yes...........

Physically yes, mentally no. Hopkins had everything to prove while still in his late thirties and he still has that hunger to match up or overtake the legacy of Roy Jones. Mayweather has all the accolades and titles he can ever get. Unless somebody spectacular comes along, he has no motivation to continue into his forties

It differs from fighter to fighter based on a variety of factors including accumulative damage taken, old age eroding your reflexes and punch resistance, and your overall work ethic/commitment to continuing to strive for physical perfection. That said, as of right now I see no reason to believe that Mayweather wouldn't be able to compete at a very high level (possibly even the highest level) well into his 40s. Why? Because he's a gym rat who is infamous within the sport for his unyielding work ethic and desire to be the best. Even if his reflexes betrayed him and he had to alter his style a bit his intelligence and dedication would likely still help him carry on picking up wins well into his 40s, similar to someone like Hopkins.

Simply yes.

It's gonna be much harder for Floyd because of his weight class. The smaller guys are a lot quicker, and smaller room for error. But to answer the question, yes. You could argue that the higher classes have more pop in their punches, but I still think it's harder for the smaller guys.