When things get really quiet in the woods, I usually will sit for at least 2 hours, calling a little bit then gettingquiet for 15-20 minutes betwen calling sequences. I have had really good luck with this because most birds are done breeding the hens they flew down with around 9-10 am and they come back to where they heard the calling from. Last weekend we sat for 4 hrs in the same spot before thetom came in.

Like the others have said, don't be too impatient while turkey hunting, they have all day to look for a mate so moving around every 30 minutes doesn't really make sense.