Part of it may also be hard water out west where I was living. I wasn't filtering or altering it at all for most of those years.
Or maybe I am far more mighty than my skinny stringy arms would seem possible lol.

I still have a hard time seeing how the plastic sleeve is failing. I could see that maybe the o-ring is failing, or that maybe the sleeve wasn't tightened all of the way into the group.

I have a brass piston, and it certainly hasn't caused any problems. In fact my current sleeve was replaced after I switched to the brass piston, and as of now I have more years on this sleeve than on my original.

I don't know why it fails. Several times it probably was just the oring but I changed it anyway because it's always seemed to go out not long after.

If these were normal times, I would invite you to bring it over so I can have a look. It might be worth sending to Stefano's Espressocare in Southern Oregon. The cylinder shouldn't fail like this. You can probably send just the group for inspection.