I should have clarified: by stable I didn't mean "reasonable work life balance" or other definitions, I meant the knowledge in the discipline you're practicing

I should have clarified: by stable I didn't mean "reasonable work life balance" or other definitions, I meant the knowledge in the discipline you're practicing is itself stable. Several of my high school friends are not physicians and, while they have to generally keep up with the latest best practices in their specialty, most of the knowledge they acquired in school never changes for the entirety of their career (so ageism doesn't basically exist), which isn't even remotely true in software engineering and it's a constant source of stress like I initially described.