I'd not do a routine cleaning. Too much risk of damage. I cleaned the thin film off my 1975 enlarger's filters when setting it up for my kids last year, but there was no change in printing times. I usually only clean them if I'm in there for some other repair. Then sometimes not. When I opened up my 1992 Durst CLS2000 head for repairs I left the filters alone. Especially since replacing a broken filter could easily amount to more than I paid for the entire head.
I was cavilier about cleaning the filters on my first D5500 back in 2001, but back then one could easily get replacement filters in just about any size from fpoint. Right now I know of no source for generic replacement filters in appropriate sizes for enlargers. (statement proven wrong...see below)