I stretch out combinations on the greenways out to 50 mi. One day I was putting my bike away and a guy I see frequently (ok, I've passed him a few times) - my out and back was 32 mi, and he rode 36 doing one segment twice (out and back twice). If you're riding for exercise and enjoyment, enjoy the same scenery and don't run into traffic problems, knock your lights out. One reason I like the longer ride is I spend shorter distance and time in the more populated parts of the greenway. Over that 50 mi, I have two different start points that will give me two different but overlapping 32mi rides. One of them I would never take on the weekends for the pedestrian traffic.