Calzaghe? He didn't even throw punches. When you toss a slap at your opponent with nothing on it it doesn't drain energy. If every boxer fought a moronic slapping style that relied on british stoppages, everyone would have the "AMAZING WORKRATE" of Calzaghe. He wasn't a special fighter in any way.
Name a boxer besides Pacquiao who could throw like 700 power punches in a fight and the last 100 are just as hard as the first. Among modern boxers it's pacquiao.
My lifetime? Mayweather Pac Prime Ouma Prime Margarito Joe Calz Pac gets the nod for me because he has a much higher energy style then the others do.... in that he throws a lot of punches AND his punches aren't arm punches they are power shots. Takes more out of you to throw with mean intent then to throw routine touch punches.
I agree that a low volume/intelligent pacing should exclude you a bit from this criteria. The two that come to mind that were constantly swinging for the hills from 1-15 are Henry Armstrong and Marciano. Having said that, Pacquiao is/was amazing though......
Monzon smoked a pack of cigarette's a day yet ran miles and easily could go 15 rounds. The man had monster stamina and conditioning.