The one I called up in November took 30 minutes to show. Once you have the time and effort invested in getting to a good location, then calling for 30 minutes, I would not leave before an hour. I'd call, off and on, for 45 minutes, then wait silently the last 15 minutes. Cats have a tendency to show themselves when they can no longer hear what they were responding to. They also, in that circumstance, like to get to where they can see what's going on. That may make them visible to you, rather than concealed in the brush, rocks, or trees.