I understand, seems like we've been talking about different things in the same thread.

There's another factor to consider though: a lot of people (me included) also lose their enthusiasm and energy very quickly whenever their hobbies become their full-time job. Up to the point they start really hating what they liked to do before.

Anyway, as I said, I'm not *that* old but, in my 30s, I already have decided I will stop working as soon as I have a chance, i.e. have enough money to spend throughout the rest of my life. Meanwhile, I know a guy who, in his 40s, earns 2 or 3 times more than me and keeps saying he loves to work and loves his job position (senior Java developer). Not sure he'd necessarily go nuts otherwise but he had some mental problems in the past, so maybe focusing on the work is a part of his therapy.