I'll grant you premature retirement is not a good thing (though it can be, if the buyout is attractive enough) and changes the equation. That said, I stand behind my point. If the knowledge in your head doesn't exist elsewhere, you can make decent extra income in retirement. If you were FORCED out of that job by a stupid company despite having irreplaceable knowledge, you can charge them an asshole tax.
One of our technical sales guys is retiring next year. He already has multiple contracts lined up for his consultancy (with us and some of our customers). We'd be happier if he wasn't leaving at all, but he has city miles on him and old age is a bitch.