How do you know you are doing just fine? How much of the market have you captured? How big is that market? What if you had created your business plan 5 years ago and today you did triple your sales? Would that extra 2-3 weeks of work be worth it?
I'm pretty sure they just look at their bank accounts.
In all seriousness, there's doing fine and being greedy. There will always be a step to climb, a market to reach or revenue to grow. The goal is to do enough to enjoy life and be comfortable, not to be the richest man in the world. At some point, you can do "well enough" and not worry about what "could have been".
My point is this: Though they may have taken Jeff Bezos on for his expertise, Bezos made his investment to earn a return. You don't invest in private or public stocks in a capitalist world to do just fine. You don't start a business for that reason either. That's not greed, that's entrepreneurship.