One should also keep in mind other mechanical issues than corrosion, remember. Corrosion is a good benchmark with respect to whether or not your cleaning habits are sufficient, but it's not the only one. I mentioned function, but wear is a long-term issue as well.
Lots of people focus on the short term...i.e., function and reliability. However, with proper care small arms shouldn't last just a few years or decades. They should last generations, and this long view is as important as any other consideration, when it comes to our heritage and rights.
Regardless...take proper care of your firearms and they'll take proper care of you.