And a number of people I've known have stopped working long before a billion dollars was in their portfolio. The consensus these days seems to be $6 million. That much being managed by a decent finance person would give you an income equivalent to being paid $200K/year[1] and you can can vacation somewhere for a couple of weeks a year and spend $6 - $10K on your vacations.

[1] it gets tricky since when you're being "paid 200K/year" you probably pay 40% in income taxes and disability and you get health care paid for so you actually take home less than that.