... I'm thinking of questions like "what supplements for Game X are in print?", or "who's the current publisher of Game Y?".
It seems to me that there are two ways to go: allow these questions but require/hope that they be kept up to date so that they record information as it develops through time; or, close them as too time-limited in scope and not useful over the long term.
That sort of constantly-changing information seems best suited to a venue like Wikipedia. For example, see the production history for Shadowrun, and the history of Earthdawn. I'm not suggesting that in all cases Wikipedia can tell you whether a product is in print or not, but it seems like a more appropriate place for that information to live.
Since answers are ultimately editable if you saw an answer that had fallen out of date couldn't you go in and edit it with the relevant information? The who is the current publisher might not be as good of a question but you could update an answer by stating "up until X/X/XX Publisher Q handled Game Y but now Publisher Z handles it."
I think it'd be to our benefit if people knew we had a dynamic community willing to keep track of such information.