I have a very good book (reportedly a classic) on sailboat rigging:
"The Complete Rigger's Apprentice - Tools and Techniques for Modern and Traditional Rigging", by Brion Toss, International Marine (a division of McGraw-Hill), 1998.
The matter of corrosion of stainless steel fittings is discussed at some length, starting on page 275. Basically, crevice corrosion is the issue. The mechanism is lack of oxygen in confined spaces, such as between a stainless steel fitting and the thing it is bolted or crimped to.
The general solution is to fill such spaces with a compound he calls "slush", which is composed of 6 parts stockholm tar, 3 parts boiled linseed oil, 1 part Japan drier, and 1 part spar varnish. I assume that this is a traditional recipe, handed down in one form or another since the age of sail.
Also widely used is straight lanolin.
I developed a similar trick in the 1970s to slow automobile battery-post corrosion down: I smeared the post and the inside of the clamp with silicon dielectric grease, pushed clamp onto post, and tightened. This ensured that the space between post and clamp was filled with silicon grease, preventing wicking of acid into that space. I should have patented it - now kits to do the same are in every auto parts store. But it seemed too simple and obvious. I bet a thousand people had the same experience.
The author also addresses stress corrosion and metal fatigue, largely in the context of failure swaged connections between fittings and wire rope. The general solution there is slush plus better mechanical details.
Anyway, I'd recommend that people read this part of the book for the practical experience and advice.
Joe Gwinn