With a nod to ppilotmike?we share the same bottom line opinion.
Apart from major contributing factors such as storage or environment, the decision on whether to prime or not, or how much, comes down simply to what satisfies the builder. Pride of accomplishment is a major overriding motivator in homebuilding. So the real number one question is almost always, what do you WANT to do?
All the debate about unprimed aluminum airplanes that are a half-century old and still airworthy - still flying, are noted and appreciated. However, has there ever been any data to support the conclusion that priming is a wasted effort, as some claim? Many people have cited the fact that there are thousands of airplanes parked outside all over the world that are decades old, are not primed inside and are not corroded. Good. That?s all very true, but it isn?t data.
The question that arises, but which I have never heard voiced, is this: How many airplanes of the same age and history have long since gone to the scrap heap because they were shot through with corrosion? Is it in the thousands? Anybody counting those? No? If there were numbers to work with, the quantity of good and airworthy vs. bad and rotted, we could come up with probability figures?data. Lacking such data, the argument against priming by reference to the existing fleet is only anecdotal at best.
The bottom line is going to remain. It?s your airplane. What makes you happy?