What drives the inevitable shifting of the timeline we use here to consider content vintage? Who makes the decision and on what basis?

I think it’s worth hearing from the deciders because the forum discussion of it obviously reflects only the views of the active minority.

A starting point:
http://www.myarchives.net/showthread…ull=1#post4680 [Rabbit1]
and
http://www.myarchives.net/showthread…ll=1#post22973 [Mushashi7]