Is it my imagination or do the black DSE901b (rn4075) seem to last longer and outperform the white DSE 901's? Could be just cuz my white one's are older and I forgot what they were like new, but since I got my black ones, my white ones are all collecting dust. They are all relegated to the emergency bin (and I even have some new ones sitting there). While these 3 black ones have been in constant use since I got them....