Here's a great example of why I keep my files in a Photoshop format.

After showing my work in progress to an illustrator friend of mine he kindly pointed out some concerns he had with some of the elements. After brief consideration I had to agree with him and I proceeded to make some changes.

I painted out the freezer door on the refrigerator and then popped the image back into Photoshop where I rotated the robots eyes down so he was looking at his chest. I think it works much better this way.