Here a confusing suggestion:

New Member
< 10 post

Observing Member
> 10 post

Member
> 10 posts and (4 post in last 30 days or > 2 Thanks in last 90 days)

Guru
> 40 Thanks total or (> 40 posts total and (> 20 post in last 30 days or > 10 Thanks in last 90 days))

God-like
> 100 Thanks total or (> 100 post total and (> 50 post in last 30 days or > 25 Thanks in last 90 days))

The actual numbers of thanks and posts is somewhat arbitrary & should be adjusted to reflect other members opinions.

Even though it's confusing, I think a valuation scheme like this is a good balance between recently joint member who jump right in contribute quickly, valuable long time members who have been unable to contribute due to recent external circumstances & the other active members to this forum.

For example, I would I consider myself an observing member to this forum. I read it 3 time a week, but I don't contribute often - therefore I'd give myself a label of "Observing Member". If I decided to contribute more and those contributions where valued by other member (by Thanking), then I would be rewarded with a higher member status.

So thank me for this contribution so I can be rewarded.