Burnout is a real thing, especially if you're still below retirement age and it's not "what you do". Just because you like baking cookies doesn't mean that you can run a bakery... there's a lot of things that can get tedious and boring after awhile. In my case, I'm not a kid anymore, and I actually like playing with the reflow oven and the pick and place machine, so the production side of things still holds my interest. I think if it was like "Damn, I got to burn 100 boards today... I'd rather be watching The Price is Right" then it would be time to hang it up. Maybe they got to that point... they didn't view the search for alternate material sources as a "quest" anymore, plus they had other things to do.