Fun comments in the thread!
I have a pretty good memory, and on the airlines I fly most there are a number of crew members that recognise me. On a BA 780 the other week one of the CC (that I immediately recognised and remembered the name of from OSL-LHR three months earlier).
I recognise about 25% of the SK longhaul crew, but SK crew are notoriously bad at recognising pax unless it was less than a month since you flew with them.
I was rather surprised last month on JL HKG-HND (C) to have a CC remember me from SIN-HND last summer in Y. I didn't recognise them! May have been because I was asleep for most of that red-eye.
I realise this post is a bit OT as it isn't CX focused, but I fly too little with them to be remembered

Only like twice a month - and a very good mix of routes.