At present a close vote is “time out” after so many days, therefore a question that gets a few views per day is unlikely to get enough close votes.
I think it would be better if a close vote was time out after a given number of users with closing powers have viewed the question – this way the system will adapt to the viewing rate of a question and cope better with old questions.
(The number could be chosen based on the a multiple of the mean number of views it takes for a question to be closed and tuned so that very few questions that were closed in the past would be missed.)
This would also reduce the need to "flag for mod" old questions that are now off-topic.
So far about a third of the people that have viewed this question have up voted it, so am I on to something here?