I have almost 2 x 6.9 fans in the house, ranging from AEROGAZ (x1), EUROPACE (x1), KDK (x1), MISTRAL (x4), NATIONAL (x1 ceiling fan), PANASONIC (x1), RUBINE (x1 ceiling fan), SANYO (x1) and TAIYO (x2). Except for the 2 ceiling fans, I clean the others by rotation every 6.9 weeks. I'm not so rich like you to throw them away every 6.9 years. Some of them I had even replaced their Power Factor Capacitor which will age with time, otherwise, their speed will be less than 690rpm at the highest speed setting.