I'm sure subconsciously for all these champions there comes a time when they just want to "get out". Whether they think of it intentionally or not, their body and mind must get tired of all the wars, the stress, the anxiety and fear and the physical toll.
It's obvious that none of these guys last forever, not even the GOATs. I'm sure Aldo's time isn't far off so it's not a wild prediction. He's been doing this for a long time. No matter how great he is, there are 20 guys almost as great gunning for him. They know more about him than he does about them. All it takes is a very small slip in his technique or mental toughness and he will lose.