It can take me an hour or more to do a page. It depends on the mood I am in. Usually when I start a layout, I finish it the same day.
My advice is to make sure you have a enough of what you will be working on. There is nothing like being in the middle of a project and run out of adhesive or another piece of paper you were working with....and do not glue anything down until you are satisfied with the page! I think 2-3 hours is perfect. Just have fun with it! The most important thing is scrapping your story!