Board Thread:Theories and Speculation/@comment-30241447-20170409050955/@comment-734582-20170409104645

Ravenlot 27 wrote: We don't know how much time it takes for the beast to revive itself after the death, there's no guarantee it'd take years, and I think that throughout the series it was implied it doesn't take that long. When the Raikage thinks of killing Naruto, it's apparently long enough to thwart Obito's plan. "not that long" is a largely subjective statement, considering the Biju are a thousand years old.

I mean, it's clearly not a pleasant experience as Kurama preferred swallowing his pride and helping Naruto over straight up dying. And if he calculated naruto's odds to be low enough to be soon free (which he nearly accomplished versus pain 3 years later) it stands to reason that his regeneration would take a similar amount of time. Probably not exactly 3 years, but in the order of a year or more. We also don't know how they regenerate, IE do they reappear at full power immediately or do they reform earlier in child-form and then restore power over some time (which also explains why they would hate it, since it would leave them vulnerable).