Redharley

I have a new pair of old Klispschorn speakers. I read in the on line owner's manual that the speakers should not be tightly positioned in the corner. Your commentary is contrary to the factory instructions. My room is 15 feet by 20 feet and the so called sweet spot is about 10 feet from the center of the wall the speakers are positioned on. Also, the speakers I have are 1975 vintage or so. Should I have to be concerned with some maintenance to permit prolonged life or even better than the spectacular performance I am getting? Thanks, Bob, Salt Lake City