> The rational choice is to sell.
If you as the owner are already wealthy 'enough', then that is not necessarily the rational choice. It depends how much you care about the future of the business.
In my dreams, if I ran such a noble business, I would hope that I'd have managed to extract enough value from the business to arrange for my own pension by the time others want to acquire it, so I can reject their offers and keep control to safeguard the business's integrity.
On the other hand, we are human. If the acquiring party makes an absolutely life-changing offer, it may be hard to resist. The story of Nullsoft and AOL comes to mind.