We have, I think, averaged one every 3 months or so.
It takes a bit of setting up, maintaining interest, organising sides (with the inevitable shuffling of squads to try and keep same clan members together in squads where possible).
A lot of us have full time jobs, wives/gf's & kids. Basically RL commitments and it's time consuming setting one up.
I'd say it'll be early 2008 (possibly post 0.7 release) before the next one's good to go.
Watch the PR forum or check
.:iGi:. Forum for news on it
BTW, all are welcome.