In my immediate area, there are only "rises", no hills. In some of the surrounding area, there are some "hills" but nothing that calls for drastic changes in gearing to overcome. But most of the area I ride has no hills. It was on a recent ride that I got to thinking about SS...I never changed gears on the whole ride.

Fixed gear...well, I don't know about that. I can't remember ever riding a fixed gear.