The exercise bike probably isn't a bad way to spend a lot of hours in the saddle, its not the same but still its usually just the sitting on my ass for lots of hours that kills me and not the exertion. You could always see if you can put your actual bike seat on your exercise bike just to keep the sittin parts in shape.

Back in middle school and parts of high school I used to ride from my folk's place along the old seward, up rabbit creek road, over on hillside, then back down huffman to get home. It was just over 11 miles with some good hill climbs in it. Anyway, you can make loops and all kinds of variations of commutes without too much trouble there.