I'd go nuts if I had to redo pages with that many details but that depends on how much experence one has cause I kinda would take longer than that. Say, do you make thumbs of all the pages before doing a final layout?
Always fun to watch videos like this one. Like a one-way express into somebody elses noggins, heck yeah.
How much time does it take you, if you don't mind sharing, to take a page from start to a polished finish? I took a look at Ravine a little while ago, and while it was a good read, as a hobby artist with a tendency to shrink work it kinda made me weep on the inside. It, uh... it looked like a time consuming work to complete xD