Geez, I barely even ever wash my bikes.

I ride year round in all weather. Winter and salty roads are a different story but I don't worry about rain hurting my bikes. Fenders are a good idea to help keep grit out of the drivetrain. If you lube your chain periodically and actually ride your bike (so that the lubricant also ends up on the cogs on your cassette) that is usually enough to repel the water that could lead to rust.

The items most susceptible to rust are those made of steel and are not painted (or lubed). Things like bolts and screws. If you're worried about them, you can put a thin coating of oil on them or even get some stainless steel replacements from the hardware store.

Cables are typically stainless steel these days.

What I ride most of the year is an almost 30 year old fixed gear conversion. It's steel and the frame has some nicks and scratches. The logos are wearing off in places but when cleaned up it still looks pretty good. Off hand I can't think think of any rust on it.

The winter bike is only a few years old. The frame is aluminum and the fork is carbon so no rust worries there. The pedal spindles are rusting and so were the bolts the hold the front disc rotor in place. Even though it was stainless steel, the front brake cable was covered with corrosion. The dust cap on the IGH has some rust and so does the front quick release. Last year's chain was shot. Otherwise it isn't too bad. This rust was from salt, - not rain.