I does sound like you are visiting to much. I personally put out the corn and camera, come back in a week. If not much activity than I move it. I usually find that putting out a mineral block takes a lot longer for them to come to, but when they do it is a hot spot. With mineral blocks, I usually put them out for about 3 weeks while I have my cameras elsewhere, then if there is a lot of activity after 3 weeks I'll put a camera on it. They seem to like the minerals a lot more once it soaks in the ground from rain. With corn, if they are in the area they will find it in a couple days.