I dont speak for everyone, or anyone really but for my self. But I think the longevity of the site has to do with how diverse everything is. I mean just look at the types of music represented here... And for the most part there is some structure to the discussions. Which keep things running smooth...
Oh and the music is amazing., that could be another good reason its stayed around. Every couple of days we have another track amazing in its own right.
But thats just me..