I ride 18 miles/day when I do commute. I do that on a 28 year old bike . . . my first 10-speed. It is scarry as hell playing chicken with the Metro busses and the SUVs. I live in Cincinnati and it is hilly here. My elevation varies from 860' asl to 500'. I know that I need gears on the hills on which I have to ride. Perhaps others could do it on a fixed bike, but I'm a whimp.