from what I understand about them:
the rechargeable vibes last as long as they are rechargeable - your guess about how long that will be is as good as anybody's.
the battery operated vibes last as long as the motor works. again, your guess about how long that will be is as good as anybody's.
maybe researching online about this might give you some solid info.
and as an FYI, rechargeable vibes are always more expensive, and some have a fairly comparable battery operated alternative.