One thing to add. My experience here in Alabama is that 9-10 am is the "Magic Hour". It always seems that when I get on a bird at that time that he is going to be alone. My guess has always been that most of the hens have gone to nest by that time.

If a courtesy gobble is all I get and he doesn't want to answer another call I may not always wait long. There is another lonely bird just over the ridge.