Well, I guess you'll be done when you'll be done - the most important thing is to be satisfied with your work!
Now, I know that when I'm struggling with a deadline for a comic or an illustrated novel or something, I tend to draw all of the pannels / illustrations that have lots of things in common at the same time - I first sketch them all, then line them all and finally color them all. If the pages contain a lot of the same characters or backgrounds, it makes sketching, lining and MOSTLY coloring way faster, since I literally color all the canvases at the same time - I apply one color to all, then the next one and so on.