Good question!
As far as the story, Katie and I have plotted out a rough script for the next two years. However, given the nature of character evolution in a story, it is not uncommon for some dialogue to change last minute. (This is usually Katie's doing. =P)
As far as a page... well... that depends... I guess, on average, it takes about 4 hours. This includes drawing, flatting, toning, backgrounds and then lettering. Katie may blame any unusal delays on my World of Warcraft habit. ¬_¬'
-Jodon