I don't think your link to your comic page worked!!
Anyway, for me, it really varies.
I found that if I thumbnail my pages first, the entire process goes a lot quicker because I already have an idea of the compositions and don't have to fiddle around with everything much.
It also depends on what type of background I'm doing. If one of my characters are speaking and it's just their face, I can whip up a blurred forest background in 10 minutes, but if they're actually interacting with the background, it can take more like 1 or two hours.