I don't know how long it takes. When I first start out, I start with one or two chapters to get me started. As the story develops, I add to it until I have everything worked out and then I plot through a close to the end as I can. And sometimes I add new chapters along the way so I try to separate chapters with squiggly lines instead of numbers.
When I get ready to plot through the end, I'm sure it takes a few hours, I'll usually work on it off and on throughout the day.
Each chapter's summary varies...bouncing back and forth between vague and detailed. Sometimes I don't know yet what I need to write so I'll just say, "So and so acknowledges the events of the last chapter and does a happy dance." Though when I get there I may change happy dance to pity party. Or leave out details that I previous set out to include, but the scene changed and I didn't need them anymore.
Still, I love having an outline, it keeps me focused and on track and helps me write faster.
However, I usually spend about a week making notes in general, sometimes two. Plot notes, scene ideas, character bios, sketches, and interviews, and this last time I drew a map and some other stuff and wrote up a quick dictionary of the Greek words that were going to show up in the story. All this gets thrown randomly into a composition book so I can take to work and sneak in bits of writing here and there. It's all quite unorganized. I have several pages of random notes in the middle of my outline. Nothing is numbered of lettered except for the chapter headings right now, which is messy because I'm adding to it as I go.
I used to rewrite my outlines as they changed, but that takes too much time. I rather just squeeze the changes in the margins and mark stuff out.