People don't like forums that don't seem very busy... so here is an easy way to make your look busier than it is.
Edit the stored procedure yaf_active_list
change
delete from [dbo].[yaf_Active] where DATEDIFF(minute,LastActive,getdate())>5
to something like
delete from [dbo].[yaf_Active] where DATEDIFF(minute,LastActive,getdate())>30
This way the number of people on your forum will appear to be more as their database session info will last 25 more minutes.