I am rotating five (65mm). They all look alike, so yesterday I used color-coded stars to rank their performance. The oldest is three months. One is not as good as the rest, and the two newest are the best. I often switch out before the light flashes, too. After that experience, I started daydreaming about the X2. Are you aware that the light on the charger turns green before the light at the end turns off? I try to get a full charge, but at times the charging station can't keep up.