Pneu, I am impressed! I seem to break my pens about once every 2 years, so I am very impressed with the longevity of your pen!
I don't change mine that often either. there was a thread recently discussing...and it really is do what you feel comfortable doing. I have heard it said that you can cross contaminate the sample..but personally think that this is rubbish...even if you did contaminate one test with another test, it would make no difference to the result.
Hygiene, to me is the reason to change, and, as my pen lives inside my meter wallet, and doesn't contact anything other than me, I don't feel the need to change, as I am healthy etc. I would change it a lot more often if I had an immune problem though! I would rather the NHS spent its money on test strips rather than giving me 8 lancets a day. If you are not comfortable about reusing them though..don't!
Edit to say I am talking about cross contamination between samples, not people.