This would depend. If someone states they are away for a week, then clearly 3 days would not be reasonable. If someone disappears entirely and you don't get any response for a week, obviously that is unreasonable. However if you put in a request on 23rd December, and haven't received a response by 4th Jan, that's entirely reasonable, as its Christmas. In addition to that, if its something that may take some looking into, that may take more time than someone just asking if something is possible.
In short, there is no simple answer to your question.