It's almost impossible to refuel above 22,000ft, especially if you have any external stores. The tanker is supposed to be at 200-210KIAS for A-10 refueling. At 25,000ft, that equates to 250-260KTAS, which is pretty fast for a loaded Hog at altitude. You have to use lead pursuit to rejoin on a tanker, otherwise you'll take too long to catch up at any altitude.