I think what DMN and I have is a different definition of "old school". I think the idea that to be "old school" all you have to do is be an 80's rapper or hip-hop group is totally bollocks. You have to acknowledge that the "old school" of yesterday is going to become the "ancient" or "super old school" of tomorrow -- and hip-hop seems to have a shorter lifespan in that regard. To me, "old school" is defined as being something/one/group that regarded as being classic(s) no matter if they were releasing albums in 1988 or 1996. Yeah, there's gotta be a cutoff somewhere (I'm not going to be calling albums released in 2002 old school any time soon), but albums released in the early 90's could easily be considered "old school".
For me it's about lyricism, beats, style and whether or not the group set a precedent more than anything else when I think "old school", and I can't think of many rappers or groups that have done that since the mid-90s or so.