With websites, they are all a phase anyway and people will find different uses for the web, hence the evolution of myspace i feel is just a fad. The social networking sites are great for now, but soon they will turn into something else. much like forums.
However i feel that a website that offers more than just what everyone else is doing and stays to their roots but enhances that will stay around for a much longer time.
I dont see this as an issue for the 350z site as yes they will stop production at some point and move onto a 400z, however people will still own 350z's and enthusiasts will still be around.