Er... actually, my DSN has!! She asked me once how often I changed my needles - only when I change the cartridge says me, slightly ashamed. Her response was that ideally I should change it every time, but she was aware that would be a hard habit to get into, so if I could aim to change them at least every day, that would be better than nothing!! I think, for some of us, re using needles is also a hang-over from the days when pens first came out and the needle-tips weren't free on prescription. I know that's where I have picked the habit up from!