SPN is by far the most maturest discussion forums on Sikh's and Sikhism.......sikh-history.com used to be good but seems to be very quiet.
What you find with Sikh Sangat is that one or two people are prolific posters there. The average age of people there is about 13, and many of them actually know each other in real life. So what they are in effect doing is publicising converstaions they may have privately on the internet......
Many people here are mature adults and do not have hours and hours to spend posting messages on the internet like 13 year olds....
In order to keep a forum alive new members should join and contribuite to forum from time to time.i have seen many sikhi forums which are dead but had good discussions earliar
Also i don't think that average age is 13 on sikhsangat.its too small to have mature discussion.