Were short subjects / short comedies ever shown again in theaters after their initial release date?

BlueWhale: I believe the answer is "possibly." As I understand it, when movie theaters showed shorts before a feature prior to the mid-1970s, typically they showed whatever shorts they were sent by, or could get from, the distributor. As explained at http://www.laurel-and-hardy.com/films/talkies/blotto.html, MGM decided in the late 1930s to reissue some Laurel & Hardy shorts from earlier in the decade, one of which was Blotto, re-released in 1937, albeit with some censorship edits. (The plot of Blotto revolved around drinking liquor during the Prohibition era when the film was originally made; by the time of the reissue, alcohol was legal again but the Production Code was in force, which provided that "The use of liquor should never be excessively presented.") So it seems plausible that the MGM distribution depots might still have Blotto available in 1939, if a theater requested a Laurel & Hardy short to show with a feature. But if you were a moviegoer looking to see any particular short subject in a theater, I suspect you would have had a difficult time doing so (even a newly made short, not just a short from a previous year). From what I've seen of old newspaper advertisements, the shorts didn't tend to get advertised. Maybe there were signs or posters promoting the shorts at the theaters themselves, but as far as I can tell, not in the newspapers.

Wow, great answer! Thank you so much gromit82! A follow-up question I should have continued with in my original question... I've been searching to see if any 8mm prints of Blotto were ever made for rent or purchase around 1937. I know 8mm prints of Blotto were sold in later decades. I'm interested in it's earliest home movie 8mm print release date. Not for purchase (it would be expensive) but for research. Thanks again gromit82. This is a great forum! :)