OK, I see many experienced GM threads. Been with OOTP since version.....blah blah blah. Looking for a good league. Well most of the good leagues don't have to look thru these experienced GM threads. Your best bet, if you are good, is to research. See who has been around for a long time. Scour thier forums, history, etc to see if they are an active league and one you may want to join. Check owners page to see the who's who and get references if you need em. There are a lot of ambitious commishes that start up leagues that last maybe a few seasons. But there are those who have been around for a 2 or more real time years now.
Ahh I am just rambling, time to shut up!
