Recently, we had a case over on Travel, where a moderator applied a bounty to their own question, and then as soon as that bounty expired, they cleared it (refunding the reputation) and restarted it. This happened twice on the same question.
It's also worth mentioning that the moderator self-answered the question with the "authoritative" answer, so they weren't really looking for new answers on top of that one to whom to award the bounty. The moderator in question admitted that this was the reason for the repeated bounties:
I felt at the time it was important enough and interesting for the community to track, and a few of us have been diligently updating it.
There were some other issues with doing so, such as the fact that the question couldn't be closed (there were some people who considered the question off-topic). Upon realizing this, the moderator removed the bounty and didn't restart it.
A lot of this is site-specific, and there is a discussion over on their meta about it, but this overall experience makes me wonder: is clearing, refunding, and restarting your own bounty as a moderator considered an abuse of the system? How about doing so repeatedly? How about if you're the author of the question? In my prior research, I found this past feature request to allow for standing bounties, but that request was received very negatively, so I don't think the community will take a liking to attempts to try to accomplish it.