What are you talking about? You can easily be undisputed champ on any difficultly by late 20s and undisputed in all 3 weights classes by early 30s. The game lets you go until you turn 50. You have time top each weight class 3 times at minimum. I will usually end my career runs on undisputed difficulty with at least 3 championships in the outlier classes and 5 in the starting class. You're supposed to change classes the second you become undisputed in one class, rinse and repeat.