Fewer still recall Tomkinson's Schooldays and Across the Andes by Frog, Palin classics which surely inspired his later Pole to Pole and Around the World adventures.
I enjoyed Monty Python at the time but comedy has a 'sell by'. Back then I didn't enjoy comedy from the 1920s which was 50 years old. I don't enjoy 50 years old comedy now.
"Holy Grail" and "Life of Brian" hold up especially well. I think it's not a coincidence that both of those are set in the past. Some jokes are less effective now, since of course none of it is really about the past, but much of it references mythical material that's still current.
I concur that their other material holds up less well, in part because they themselves didn't always seem to know which jokes were going to land. They had a fondness for absurdism, much of which wasn't even all that good when it was new. But some sketches, like the Lumberjack Song or the Spam sketch, just seemed to click, and still work.
It depends... I don't particularly enjoy Monty Python... But 40 year old stuff is still seemingly great in places. Like Yes Minister and Blackadder... I do not think those will be too dated in 10 years still, unless something very drastically changes... Maybe some are just bit more timeless...