I sail in the Chesapeake Bay (US) and it's tributaries, which I think is more brackish than salty in the part where I am.
It's a glass covered wooden hull, with a copper bottom, and any metal outside the hull is brass, copper, aluminum, or stainless. The boat first sailed in 2011 and I haven't done anything to it. The copper bottom has browned some, but I wanted that.
I oil what ought to be oiled, especially the stainless rods that hold the external ballast to the bottom, salt-water or not.
If you have ferrous metals on board, wiping them with machine oil or PTFE after a sortie is never a bad idea. Same goes for the stuffing box and other moving parts.