There are many caveats to this however such as rust forming during storage, dirt entering the engine etc. There was a good discussion here a while ago regarding air filters on engines - I use them all the time. Dirt entering an engine during hovering (especially) and flying can cause scratches on the piston/cyl not necessarily the carbon.

Bearings will eventually wear and should be replaced when they no longer feel smooth. They develop a kind of notchiness evident when turning the crank by hand. Obviously you must remove the engine to feel this.

Lots of folks use some kind of after run oil after flying to mitigate the rust factor. Nothing wrong after flying, with loading up your engine with oil or some kind of after-run oil. Just be sure to remove the plug and turn the engine over before starting the next time or you can easily break pistons, connecting rods etc.