Why is it not possible to offer a bounty for longer than 7 days?

Question

I had offered a bounty for the following question that expires in 7 hours:

What did Gelfand mean by suggesting to study "Heredity Principle" structures instead of categories?

The results have been very disappointing. No answer was added, no comment, no reaction at all. Which leads me to the conclusion that the limitation of 7 days may not be suitable for a bounty to achieve its goal.

Especially when a question may require some longer thought or when people don't check this site regularly.

I imagine the limitation of 7 days comes from the Stackoverflow.com site, whose activity level and status of professional importance are completely different from Mathoverflow.com. While the 7 days might be appropriate for the former, it may not be so for the latter.

I hope for some consideration towards increasing this limit. With the current 7 days limit (which I regard as a too low for the system to work as intended in some cases), I will not offer any bounty again and will not recommend it to anyone.

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UPDATE. When writing my response below to the answer by Joseph Van Name, I have looked at the 6 bounty questions and wrote this answer that the OP found helpful and awarded the bounty, even though my argument was incomplete to solve the problem posed.

Did the system work as intended in this case?

On the surface yes, since it was the bounty through which I have discovered the question.

However, it was a huge coincidence that I had found it, as the bounty was about to expire within a day! Had I looked just 1 day later, I would not have discovered and answered this question, with the bounty of 250 points would have possibly lost. In contrast, chanced were much higher if the bounty stayed for somewhat more reasonable period, especially given the coming holidays.

Now this leads to the question, how many similarly interesting questions are still there unanswered and undiscovered during their short bounty period, precisely because it was so short?

And finally, analysing a bit deeper the effect of the bounty on that question, it is clear that even there it did not quite work as might have been intended. As my answer did not completely solve the problem, it would have been again more beneficial to have the bounty for a longer period, that would attract further contributions to complete the solution.

Answer 1

I consider the 7 day bounty period to be quite reasonable and effective for several reasons.

1. While bounties cost a minimum of 50 pts, in reality the cost for a bounty for one's own question is much lower. If you put a bounty for a question, then that question will receive more upvotes than if it did not have a bounty in the first place. One should consider the cost of a bounty to be more like 25 pts. A 7 day bounty period for 25 pts is therefore a very good deal since a person who answers will still be rewarded 50 pts for a correct answer within the timeframe.

2. The purpose of a bounty is not simply to give people extra points for a correct answer if one gives the answer. If the purpose of a bounty were to simply reward a good answer, then a longer bounty period would be more understandable. However, the purpose of a bounty is in part to give the question more attention and to signal its importance. When I have given bounties in the past, I have considered the 50 pt investment into the bounty to be a very good investment even if the question has not been answered simply because the bounty gives the question more attention.

3. If you would like to offer an entity points when it gives a correct answer, then you may freely give your points for that answer as a bounty after the question has been answered.

4. A longer bounty period will simply mean that every individual bounty question will be given less attention for the time that it is a featured question since there will be many questions with bounties to choose from. This sort of bounty inflation will defeat the purpose of having a longer bounty period.

5. A longer bounty period will not guarantee that anyone will answer the question. If a question has been unanswered for 7 days, then it is unlikely that such a question will be answered within a month. Some questions are not answered because they are difficult.

6. In the case that a question goes unanswered after the 7 day bounty period, one may put up another bounty to that question. The 7 day limit is only for those who do not have enough points to pay for multiple bounties. If multiple people consider a question to be important, then those multiple people can each offer a bounty on that question.

Since the Hereditary Principle question has 38 upvotes and over 1000 views, it seems like people are in fact interested in such a question. They simply have not come up with good answers.

Answer 2

I would like to address the points in the extensive answer by Joseph Van Name (EDIT. unfortunately deleted by the author), that would be too lengthy to put in comments:

1. In case of my question, all the up-votes occurred before the bounty was assigned. Then, not a single up-vote was added as the result of the bounty. This disproves the suggested effect that the up-votes attracted would compensate for the bounty. What this also likely means, the bounty did not attract any further attention. In my interpretation, the reason is that active users have already seen the questions, whereas a bounty of 7 days does little to attract attention of less regular users, who could provide additional valuable insight.

2. I would assume the ultimate purpose of the bounty should be to encourage quality answers. If "attracting attention" only refers to further up-votes and views without any tangible activity, I would question its usefulness, and would not feel compelled to ever offer a bounty again. In my view, the prime goal should be valuable activity, whereas attracting attention is merely a byproduct effect. It is the former that we (I) want to reward, not the latter. Especially if it will take time for the person to write a good answer, I would like to reward it.

3. I did not know that it was possible to assign reward after the answer. However, this way I would still lose valuable inputs by busy people, who might have been more compelled to take the time if the reward was declared beforehand. That way my bounty still fails to achieve the positive effect I am aiming at.

4. At the time of writing, I can see 6(!) featured questions in total on the Mathoverflow site! For the whole mathematics! With none of them even close to my area, just to put it in a context. I would hardly call it "too many questions with bounties to choose from". In comparison, the Stackoverflow site has 366 bounty questions! That I can refine by selecting the database tag, to get only 2, which explains how the 7 days over there makes perfect sense. Whereas the 6 questions in total on Mathoverflow, also explains how the 7 days there is way too short. In fact, working with the ratios, we arrive at $$ 7 \ {\rm days} \times 366/6 = 427 \ {\rm days},$$ to reach the proportion of the SO.

5. A longer bounty period will very likely increase the chance of an answer, because the question will get more likely noticed by more busy people who only come here sporadically. In contrast, the 7 days period will be of little effect for anyone in this category.

6. Being myself not a regular user, I probably fall in the category of the people who "do not have enough points for multiple bounties". However, more fundamentally, when I see how little effect the bounty achieves with the current system, I don't feel encouraged to keep offering bounties, even if I had more than enough points. Concerning bounties by other people, none had been offered that far for this question, despite the obvious interest judged by the number of votes. Which might yet be another sign that the current system does not really work (i.e. is a bug).