one of the points of bankrolling is not only for a safety net, but it's also to indicate to you how good you are. If you feel like you are dominating the stakes you are at currently AND you have ~15-20 buyins for the next level then I say move up right away, because you can always move back down if you find your skill level isnt up to par with the next stakes.

I also think 5 buyins is a good swing aproximation. If you lose more than 5 buyins playing a conservative game you might have gotten really unlucky, but more than likely you arent quite ready to play at those stakes yet.