When designing color covers, if there is any possibility you may produce hard covers this consideration should be addressed when putting the file(s) together:
Anywhere the cover has high wear, such as spine hinge and the outer edge (or fold) of the cover image density is a factor if long wearing covers are a goal. While bright colors and high contrast images are traditional favorites for color covers, lower pigment density slows wear (and separation from protective lamination). For longest wear, it is recommend that these high wear areas have a combined CMYK density of no more than 260.
 This section is drawn from  http://www.gregathcompany.com/binding/art/hardcolor.html