My first UA 747 flight was SFO-LAX, believe it or not, on a PA 74L in the early 80s. I think we paid $39 and somehow got upgraded to C without asking. Of course, back then I had no idea what was what class but I knew it was a 747 SP. I probably still have the boarding pass somewhere.
I was hoping for a final flight in September but my route already converted to a 77W
So, my last UA 747 flight was in February 2017.