Interestingly, I think the key challenge is knowing when you've removed that question mark. The post attempts to provide guidelines around that, but mileage certainly varies and there are gray areas.
I think a tougher question (for me anyway) is when you have moderate, sustainable success, but not the stratospheric rise that you envisioned at the outset. At that point, the decision becomes tougher because walking away means that you are giving up something of significant value. I have also found personally that I like building businesses, but running them? Not so much.
So, the business becomes an anchor, keeping you from a greater vision/mission. At some point, you finally realize that it has to be sacrificed in order for you to get back on track, but precious years can be wasted under the illusion of success before you get there.