Good discussion here. Part of the reason smaller fighters flame out quicker is they don't have the luxury of "testing the waters" and easing into divisions with exhibition fights. To maximize earnings, the best truly fight the best and quickly. That's why a guy like Inoue became a lineal champ in less than 10 fights and already has picked up titles in two different weight classes.
There isn't another fighter currently on the Pound 4 Pound list that's fought in four different weight classes, or faced a fighter on the level of a Cuadras for their first bout in a new weight class. When Manny hit his 4th weight class, his first fight was against the easiest available champ in David Diaz. Floyd did Sharmba Mitchell for his fourth weight class debut. History might have been different if they jumped and went in with the biggest threat available like Nate Campbell or Antonio Margarito.
Even a supreme talent like Ward had the luxury of easing into 175 against guys like Paul Smith, Sullivan Barrera and Alexander Brand. What if he had to jump straight from168 in there against Adonis Stevenson?