I sort of subscribe to the same notion that Gabriel put forth. I decided to look up Patina in Wiki and I will save you the trouble by just pasting it below. Think of it this way, while continuing to ride and enjoy the bicycles you own, you are adding Patina for the next owners down the road.
Patina is a coating of various chemical compounds such as oxides or carbonates formed on the surface of metal during exposure to weathering. The green patina that forms naturally on copper and bronze is known as verdigris and consists of copper carbonate. Patina also refers to accumulated changes in surface texture and colour that result from normal use of an object such as a coin or a piece of furniture. Artists and metalworkers often deliberately add patinas as a part of the original design and decoration of art and furniture, or to simulate antiquity in newly-made objects.
Patinas are restricted to exposed surfaces and can flake off. One reason bronze is so highly valued in statuary is that its patina protects or passivates it against further corrosion. This natural patina seldom shows a tendency to flake. Brass is also resistant to corrosion, but it is, in the long run, not as attractive since local pitting shows against the shiny background.
Figuratively, patina can refer to any fading, darkening or other signs of age, which are felt to be natural and/or unavoidable.
Ray Homiski
Elizabeth, NJ USA