Board Thread:Theories and Speculation/@comment-27717552-20160513151229/@comment-734582-20160514181623

it seemed all Sennin more or less quit being ninja for the majority of their adult lives. Tsunade only took up her Medical Ninjutsu as Hokage after potentially decades of betting. Orochimaru dedicated most of his adult life to research, not ninja training. Jiraiya traveled the world and gathered intel for Konoha.

None of them were busy advancing their techniques.