When I was new to comics, I neglected the storyboard/thumbnailing process. Just planning out a chapter seemed like so much work, let alone drawing the thing. However, these days I think the storyboarding stage is the most important part, even if the production stage is the longest part.
Here's my thumbnails for chapter 4 of Etherwood:

That chapter starts here if you want to see the final versions:
Comic artists, what do your thumbnails look like? How long does it take you? I'm thumbnailing chapter 7 right now and it seems I can only satisfactorily do 2 thumbnails in an hour of focused work.
For you novelists, I presume the outline stage is equivalent. Do you pore over your outline for days? It usually takes a few weeks for me to finalize a chapter of thumbnails. I spend a lot of time thinking about how to fit the scenes together into their most entertaining form. I do my best to avoid any dry moments - every page should have a treat on it.
Also shout out to @allenT because I know you spend even more effort on composition planning than I do!