I should have seen the handwriting on the wall in ... 1991. I should have pursued a new degree then.

You were in your 30s then? That seems to be a good time for a career change. Beyond that and it's more of an uphill battle.

Yes to the last question, your guess is correct. That's the last window of time in my life I could see that changing careers was feasible and possible with good results.

What prevented me from doing something like that in those days was geek self-image. I was committed to proving I could have made a go of things. The IT and SW dev field heated up for a few years after that and I did barely alright.

In the broader view I should have recognized at that time (1990-95ish) that the hot hiring I experienced fresh out of school wasn't coming back.