That's not too much.. You're letting out two to four grunts per sequence? One episode comes to mind. I settled into a spot and once the woods regained its composure I let out two grunts. I waited one half hour based on my watch and let out a single grunt. Waited another half hour and let out another single grunt. The buck closed the last twenty yards at a trot. I was chilled and had laid my bow on the ground. Busted. As I bent over slowly to pick up my bow I heard him go. As I turned to look all I saw was a very nice set of antlers disappearing the way they'd came.
In a big woods environment where there are fewer deer, bucks might be trolling and you probably should be calling more frequently. Where there's a good deer population and you feel good about your set-up, less is probably more.
I've been calling for twenty years or so and calls are my crutch...I haven't seen it all but I've seen a lot. You never know how the deer are going to respond, you just gain more confidence from your successes and learn from the opportunities you botch.