That was part of my condition of sale I told the 3 companies before we even talked: on the day of sale, I'm gone. No consulting or anything. I had to make a clean break.
Yeah I might have made more if I promised to stay with the company, but that was completely out of the question for me.
There were no super key employees. (Some great people, but everything quite documented so someone new could step into any role at any time.) It was just a working system.
The two main techies were probably the most key in explaining the system to the new techies.
I set it all up this way to give myself personal freedom, but it definitely helped for handing over the keys to the new owner.
Being unwilling or unavailable is probably a downside. But being unnecessary is a massive upside.
Then this: http://sivers.org/book/UltimateSalesMachine