User blog comment:Njalm2/Nanja's Point of View: Shinigami Edition/@comment-25579547-20150504022502/@comment-3403804-20150504125950

A good question, in a case like that I'd say it'd depend on their conviction to that cause. Yamamoto's drive was similar, but as has been shown in the series, it was likely not real enough to support his continued existence, leading him to grow old. While Yamamoto believed in the cause, he'd grown desentisized to the suffering of ordinary humans and pluses, and by and large had stopped caring. The most powerful beings would likely have been driven to become powerful by virtue of the strength of their spirit, which naturally translates to a longer life. Likewise, the more powerful you are, the more powerful your drive needs to be to balance out that power.