The crashes started on 12/20 when I started skiing hard just as the novelty effect expired after 3 weeks of skiing. (The novelty effect from moving to NYC in 2017 expired after 3 weeks and so was the lift from starting to bike in 2018.) I was done with skiing for good after 3/2, but I still kept keeling over. 2 km walk or 3 mile biking would put me in the pound for 3 days.
I would've gone on a trip, to SF or somewhere, to lift me out of the struggle. But the whole country is under a lock-down for Covid19, and overnight trip has been out of the question. So we went on a daytrip to Lodi and Galt on 4/15 instead. I've been meaning to explore the local cities and this was as good an excuse as any.

The daytrip did not lift me out of the PEM struggle and I conked out for 4 days after that. I've written before about daytrips, unlike longer overnight ones, not being effective for ending a PEM struggle. This was another data point.
Fast forward a week, and I seem to have gotten out of the struggle finally. I walked almost 2 miles on 4/21 and then walked around the neighborhood in the afternoon the next day. Yesterday, I was able to run errands in the morning and then bike 4 miles in the afternoon. Today, I did the grocery shopping in the morning, walk a few blocks in the afternoon and took care of paper works. No crapping out despite up and running for 4 days in a row. I'm feeling as well as I did last November when I was up and running fine after returning from the trip to NY/NJ where I took 20,000 steps every other day. It sure feels like another recovery.
So, what lesson have I learned? No more season pass, that is what. I'll just buy day passes a few times next year and stick to green slopes. But then, that is what I said last year and yet I did what I did. Will the crash of 4 months teach me a lesson this time around? Stay tuned.