Ummm......about extra cylinders for quick reload. There is a slight problem of carrying and handling loaded cylinders for revovlers. Nothing holds the cartridges in the chambers while it is loose from the gun's frame. And pulling out an empty cylinder is not all that easy trying to reload the revovler.
Remember, if a three screw model, the hammer must be drawn to the half cock position. For a New Model Ruger, just open the loading gate. But you must depress the cylinder base pin latch and pull the base pin forward to clear the cylinder then remove the cylinder from the frame. Then manipulate that loaded cylinder without spilling cartridges all over the ground to insert it into the gun, line up the bore of the cylinder and replace the base pin, then close the loading gate. Not as easy as it sounds. Maybe not fast, but punching out your empty hulls and reloading is not as bad as it seems.