When you make a mock scrape, what you are doing is trying to get a buck to come in and either take that scrape over as his own or try to confront the intruder in his area. Id say you wont have much luck hunting over one until you see sign that a buck has checked or freshened the mock scrape. Its kinda like having two male dogs divided by a fence, when one comes out and marks by the fence you can almost garantee the other will do the same next time he is around. The only problem is bucks do most of that at night, thats why if you freshen it during the day it can kinda train the buck to check it during the day if he wants to catch the intruder. Id make it at least a week in advance maybe longer.