The likelyhood, especially later in the season, of getting an animal to reply may depend on the pressure of the area. I've had elk bugle in "bussier" area, but never as often as in areas with less pressure.
My buddy doesn't care to walk miles a day.
This could significantly decrease his odds. While I believe in hunting smart, as well as hard, he will likely have to put a few miles on.... or have more luck than most of us.