You’re running late. You’ve got to get one child to ballet and the other to soccer and just remembered you are out of milk so you swing into the parking lot of the local 7-Eleven. You are in and out with milk and back on the road before the kids brawl in the backseat. Convenience stores like 7-Eleven, Circle K, and Wawa continue to flourish despite a sluggish economy for this very reason—they are convenient. In fact, according to NACS, the Association for Convenience and Petroleum Retailing, in …