Half the battle is using good quality product.
I launched my 1996 boat yesterday. It will spend the next 4-5 months in the sun & in salt water. Not likely it will see many rinse offs other than what the rain provides & that is no help to the sides. The hull looks like just out of the mold, almost. Every year, only once a year, it gets the two step process using 3M cleaner wax followed by Mequires Flagship wax.
The trailer gets the same treatment with the same products only the front cap gets the attention maybe twice a year. Those acidic bugs will eat into anything & the ability to wash off the front is nowhere near as frequent as I would like.