"...post about forever"

Exactly, then it should never die.  The Fun Stuff topic falls into the same category, used to be stickied but since it is so popular, it doesn't need to be.  It's not necessarily an "Important topic," same with the Now Playing one.  The other topics there ARE important because they deal with the Kart meets, etc., but because the posts in those topics come less rapidly it is a good idea to keep it always on the top, in case a member who was not around comes to check the state of the boards.  The topic with the USA 07 meet was put there by Jones "Until I take it off" I think

I look at it like this, if there were no stickied topics, which of these thoughts would be most likely to occur by a member here in 1 year:  "I wonder what (Insert name here) looks like"  "I wonder how old (Insert name) looks like"  "I wonder what video game (Insert name) was playing on October 6, 2007"

The Birthday/Ugly Mug topics have more of a lasting historical value, a Now Playing topic is important, yes, but it has no real value after no one has posted in it for a month.  If no one posts in the Birthday topic for a month, the topic is no less important, as it contains a large wealth of information.