I signed my contract for An Audience for Einstein with Mundania in early November 2004. The paperback and ebook edition appeared at the end of January 2005.
Fifteen months did not seem excessive to me. During that time, I had input on the cover art and went back and forth with the artist to settle on the final design. I also work with my editor at Mundania to change punctuation (and other formatting issues) to meet Mundania's style requirements and "argue" other changes. (Really, the whole process was relatively painless.) The worse sticking points were a few word choices where we both refused to budge. In the end, we reached a compromise and I'm still happy with the way the book came out.
So, basically, you're not just twiddling your thumbs that whole time. You'll have plenty to do, especially as the publication date looms.
Hope this helps.