Sometimes I would like to add a bounty to a question (usually not even my own question) however I know that I won't be available in exactly 7 days to accept the correct answer. Once, I even had something come up and I had to give my login info to a colleague to accept what was in his opinion the best answer. Life sucks, sometimes we cannot help but miss a deadline.
In my opinion there should be a one-time "extend bounty time" option available to a question. This option could even expire 24 / 48 hours before the bounty itself expires, or cost the asker an additional points penalty (perhaps add half this penalty to the bounty itself). Here are some supporting arguments in favour:
Be there no mistake, I feel that deadlines on bounty questions are very important and I agree that they are necessary and should be enforced in general. However, if intelligent methods to prevent abuse can be determined, then an option to move the deadline would be a big help to both asker and answerer.
Amendum: Considering the new grace-period feature, I now longer see the need to move a bounty deadline to be as urgent as it was before. I think that the 24 grace period is a terrific solution to the issue for most common cases that I could conjecture. However, there are a few fringe cases where an extension would help so I'll not close this thread.