To me /. feels like it's been around forever. Partly that's because I was on it when I was a kid, but it felt old even then, I think possibly because its great rival (adequacy) had already died (since when K5 and Plastic are also basically dead).

I get a weird feeling when I think that it's less than twice the age of 4chan, which still feels new and exciting (possibly because I was there in its first year and have watched it grow).