I do all of one task until completed, but it'd probably come out to 2-3.5 hours per page.
My process is a bit weird though. I go through my script and draw every background in separate file so that I can easily copy and paste where needed. This is where the bulk of my time is saved in the long run, and it got me into doing more detailed backgrounds as a result. Then I go through and pencil my characters into the scene for every page of the chapter, then all the ink, and all the colors.
It probably sounds odd, but when I'm in a specific mode I get a better heads pace. I think of it as penciler, inker, colorist, letterer.