Even if I didn't have kids, I'd have plenty of things to do with my SO: hiking, traveling, cooking, etc. "Productivity" has a lot of forms, and many of them aren't marketable at all, so I really don't think I'd need to look for a job if I didn't need the pay.

If you're single and/or your friends/SO all still work, then yeah, I imagine you'd get pretty bored after a month or so. But if you already have a lot of fulfilling things you'd like to do but don't have time for, I think not working could work out pretty well.

My brother didn't get married until about 40yo and had a fantastic job (made it to VP level as an actuary), so he made way more than he could spend. He ended up being able to retire around the time he got married, and he inherited 3 kids (she's a widow). He's been retired for several years now and still finds plenty of things to keep himself occupied. He could totally work if he wanted, there's just other things taking his time.

Everyone is different. For some people, work is the most fulfilling thing, which is why we'll see many very wealthy people working into their 70s (or 90s for Warren Buffett). For others, relationships are more important, so they quit as soon as they have enough. And for others, various hobbies fill that spot. So it really depends on what gives your life meaning.

For me, it's my SO and kids, followed by FOSS. So if I didn't have to work, I'd spend more time on those, not look for another job.