Bill - You're a step ahead of me. I can't even decide what a perfect image would look like. I'll get it to a point where I am very happy and think I'm done. When I look at it a week or so later, I'll figure out something I could have done better and make the change. A few days later, I'll decide I went too far and take it back a bit closer to the original.
If I look at it again, I'll have another tweak in my head that I want to try...
I should learn to leave well enough alone...