Currently, bounties are primarily a way to draw attention to get a good answer in a timely fashion. 'A bounty is a way to get additional attention for a question by offering some of your own reputation for great answers.". When the bounty is posted, it adds the question to the 'featured' questions lists.
For programming sites that makes sense, a solution is needed and you are willing to pay extra for the solution 'now'.
Occasionally, on some sites there are questions that require either a high degree of research and/or a level of experience and knowledge that is not available in the current daily visitors. You would like an answer, you are willing to both a 'pay' for and wait for it.
I would like to propose a new category of bounty, "Standing Bounty"
It does not expire
It does not put a question on the 'featured' questions lists
It does keep the question on the unanswered list
It can only be manually awarded
If the OP does not visit the site for some time (1 - 3 months) the bounty falls away
I have a few questions on pets.se where the best answers are just not going to be quick answers from one of the existing regular members. I have considered posting a message that I would grant a bounty if an answer meeting <criteria> was posted, but it feels like it should be a more formal process.
The target is surfers who do not have an SE account and do have the knowledge (or the energy to do extensive research). I want to draw them into share their knowledge. They found the question, because they are interested in the top (i.e. search results). It is unreasonable to expect this person to find my question during the week the bounty is posted on the 'featured' list.
To clarify, the goal here is not to lead people to the question, this proposal does not advertise the question. The goal is to encourage someone who found the question to answer it. On Pets.SE we have 8k drive by surfers per day with only the smallest percentage participating, I assume other specialty sites see similar trends. I want to encourage that surfer who know the answer to my question to stop and answer it.