Adrian Peterson use to return kickoffs, and then someone realized that it isn't worth having a guy like that back there. The chance of getting a big return isn't that high, especially compared with the chance of injury on such a violent play. But during the playoffs, at the end of the game when you need a big return, Peterson still finds his way on to the field for a return.
Other guys have shown the ability to be successful on returns, no reason not to use them first. Duke is far too important to risk injury on a couple special teams plays a game. I expect at least one return per game against FSU, VT, Nebraska and Louisville. Outside of those, trailing in the fourth quarter against anyone else might be the only other time.