I placed a bounty on a very old question, to encourage new answers as it was overlooked at the time. There are a few new answers as a result, but the attention has resulted in new upvotes on both the new answer and the old answers. I said I would assign the bounty to the highest voted answer when the time is up, but the bounty is due to expire and the highest voted answer is from 2011, thanks to its recent new upvotes.
I would like to assign the bounty to that old answer in recognition of the appreciation finally shown to it.
I would also like to assign the bounty to the highest voted new answer, which I find the most impressive.
Is there a general guideline to which would be preferred?
In future I will always specify whether the bounty is intended for new answers or all answers, but since this (my first bounty) doesn't specify, I want to know the general feeling, or any relevant rules.