I do the same, but here is the flip side.

There wasa 400 acre farm myself and two of my buddy's used to hunt in exchange for doing a little work. No problem right? The thing is, he had several neighbors who were neverwilling to help him out, yet he continued to let them hunt the land. To make matters worse, these same neighbors did not like our presence there even though we were hunting on landwhere we had permission. They even went so far as to lay down roofing nails in a couple areas where we parked in an attempt to run us off. When this was brought to the farmers attention, he basically turned a deaf ear to the situation. To make a long story short, we pretty much allowed him to take advantage of our good nature and the situation became very one sided so we parted ways.