Khan's chin is worse than you think. Watch any of his recent fights, but particularly the Maidana/Peterson fights. The bell for the first round goes and Khan is unbelievably quick, people struggle to get near him. Then eventually after a round or three they land a decent punch. Khan doesn't go down but he's seriously buzzed and his speed deserts him. Guys like Maidana suddenly are as quick as Khan is.

So it's not like he's in wars because he likes to fight like that, it's because he hasn't got any choice in the matter after he gets slowed down. And there's no way to fix this. If he moves back down to 135 he's so weakened he can get knocked on his arse by feather-fisted domestic fighters. If he moves up to 147 world alphabet level he gets badly sparked. And forget about tightening up his defence, he's going to get hit at some point no matter how he fights. All he can do is remain at 140 and take part in a few more entertaining wars for whatever world-level fights Golden Boy can make. Due to his unbelievably bad chin guys like Peterson and Maidana who don't have a fraction of his skill are Khan's level in boxing.