In my opinion, I think it odd ot declare your group is active or longterm. All groups have their spans. Whether the group is active or not all depends on the member's commitment to get online frequently and keep it going for however long. Just declaring your group is active doesn't really make much sense. You can't predict a future factor, so its better to see how members take to the group first, then you can claim being active after a standard period of time. Similiar to Longjump, I've hosted a few groups, but didn't predict it's activity.
Don't give false promises, those who advertise. It's better to just say what you are about and then see how the idea flows later on. That way, people in your group are having fun, time, and no one has to say, "I thought (insert complaint here)!"