It's very exhaustive to change the lay-out of a forum. I'm done with my third lay-out (still gotta place it). But that's because I'm a perfectionist >.< (and I want to do it better....=.= so at the end I'm exhausted XD)
You should do it, when you have time I think.
I'm said every season..but finally, I do it more often...
At the end I look like crap and I'm happy for a week or two..and then..I'm not happy at all..

. I guess I'm a bit to severe towards myself.. XD
Anyhow, I have no clue, I would say whenever you feel like it...
(that wasn't helping ROFL)