Considering the demographics,and negotiations,guys dont fight as often as they used to once they win a title,so I think its who they beat,not how often they fight.
Also the investment angle screws things up as well,it takes longer to win a title, because if a manager thinks he has something he's going to take as many padding fights as he can for his guy before he'll risk him on a title shot.
Its who you beat,not how many fights you have.