This discussion is reminiscent of a lot of the recent discussions on the radio forums about the demise of oldies radio as we knew it (precipitated mostly by the killing of New York's WCBS-FM and its replacement with 'Jack' two years ago).
These channels change, sometimes out of all recognition, because the demographic target is a constantly moving one. If you want to hit the 35-54 target with the shows they grew up with, well, that's a different batch of shows now than it was back in the 1980s when these channels got started. A generation that grew up on Danny Thomas, Lucy and Dick Van dyke has been replaced by a generation that has no direct memory of anything older than Cheers, Frasier, Cosby, Tim Allen and Fresh Prince--so those are the shows they'll now program (along with the shows the current 35-54s remember as endless reruns on their local stations like Star Trek, TOS). Friends will probably be coming soon to either TVLand or Nick at Nite as well.
TVLand would now be running Seinfeld too, if that show didn't have such an amazing power of sustaining and constantly renewing its fan base in the more lucrative realm of broadcast prime-time access syndication...