Self delete or expire time sensitive questions
I have seen some good questions which were closed because they were poll/suggestions/list types of questions. (even that is debatable)
If you post a question and you think the question will be obsolete after x months, it would be beneficial if the poster can set a setting to have the question self delete after x months.
If Stackexchange sites are too concerned about having questions which will be obsolete later, this function can take care of this issue.
SO already has lots of obsolete questions that got posted by other means than poll/suggestions/list questions.
As for answeres' reps, either they keep them after the question is deleted or for the people who genuinely help others (and are not in it for the reps), the rep is deleted.