I’ve had AC filters running for more years than I can recall, still running several old school AC 500’s (110’s), and never lubed a single moving part. If the impeller shaft or impeller is running rough just clean them up . At the most maybe some emery cloth on the shaft, or replace. No need for lube unless you just like lubing things. Lol
Wow!!! That's amazing!! I'm just now discovering their greatness! Lol. What have you been using for media, though? I know it's got to be a pain buying the sponges and etc. over and over? I've tried those cut to fit filter media pads recently.