Usually, he can reset anything every time he switches form, like back when his usual body aged on the island and he reset that by transforming. I've been curious this entire time what part of him is getting exhausted. I guess "soul" huh, if he's been able to store the people he meets... It can't be anything like overclocking a human brain, because he can reset his physical attributes... But he gets nosebleeds the classic tell for overexerting mental powers. So??? Am I forgetting some piece of lore?