How much editing and rewriting is enough?

I'm coming into the final stages of work on my novel, The Color of Longing. I've read it multiple times, I let it rest for over a year, worked on it again. I had several beta readers and my agent give me feedback , and I worked on it some more. And then last summer, I declared it complete. Years ago, I read that we finish a piece of writing or artwork when we run out of time (if we're on a deadline) or we run out of juice for the project. I'm running out of juice on this one.

However, that doesn't mean I was done at that point, just done with rewriting. The next step was to send the book to a professional proofreader. She found a good number of small things and a few larger items to signal to me and I made all those changes. Then I sent it off to the designer.

Now, I'm proofreading the laid-out version. I'm restraining from making changes, just cleaning up errors, but it is amazing how many things I see each time I look at it. But after this round, I'm just going to let it go. There's a perfectionist part of me that wants it to be just so, and I also know that imperfection is part of the creative process.