When I told David that my ceiling needed another half coat or so, he told me that there was only a half gallon left and he wasn't sure if that was enough. I was annoyed because it's not my fault if he misjudged the amount of paint that would be required, but I told him I would happily pay for an additional gallon if that was what was necessary. I thought that we had agreed to that, but when the job was "done", I came home to find that nothing additional had been done on the ceiling. His crew also missed many small spots and a few very large areas as well.
To his credit, David offered to come back and fix it, but I was fed up and didn't want to disrupt my home again. I won't be hiring him again in the future.
Lesson learned not to pay until I have had a chance for a walk through, though.