I would recommend doing this if the boat is going to sit in the water without use for a long period of time or even over winter if it is still in the water. Best practice is to always rise down the boat and engine after a cruise, this ensures that most of the saltwater has been washed off and helps cut down on corrosion and rust. I personally haven't seen or heard of trim rods corroding on our boats due to leaving them exposed. Hope this helps answer your question.
