What about introducing the concept of rolling points?
As in, you get to keep points for up to 12 months but after that they drop off? (but perhaps they could be kept in a 'lifetime points' category, so you'd have 'current points' and 'lifetime points').
This would:
1. Encourage newbies (such as me) to contribute knowing that I have some chance of mixing it with the 'early adopters'. I think Thomas is way up there on over 6500 points at the moment, and thats a lot of good forum answers for me to contemplate (given my one blog effort seems to have been given the gong, how do I get points for that?).
2. It would keep people coming back to make sure their points tally ticks along rather than resting on their laurels (heaven forbid).
3. The lifetime points category would mean that long termers wouldn't be discouraged by disappearing points.
What say you?