My shortest commute is only 4-5 miles home (the longer loops are in the 12-16 range for the most part, but can be longer if I really feel like it and there's everything in between), so I'll often add distance if the day is nice and I don't have anything pressing waiting at home (like a book with only 20 pages left or something).
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Bikes: 1996 Eddy Merckx Titanium EX, 1989/90 Colnago Super(issimo?) Piu(?), 1990 Concorde Aquila(hit by car while riding), others in build queue "when I get the time"