A very good friend of mine had an old Remington Model 11 that was given to him that he used almost every day of the waterfowl season. Always in salt marshes, by the way. He is incredibly hard on his guns, and believes in cleaning, "once a year, whether it needs it or not." If a screw fell out, he replaced it as best he could. If a part broke, he usually got a new part from Numrich Arms and fixed it himself. He recently retired the gun because he couldn't get parts anymore. It had a rust patina all over it, and looked like a classic old American fowling piece. But as long as the the parts held out, it was functional.
Personally, I like how the old rust blued guns develop that bronz color as they "rust". Sort ov evokes memories of the old times. But, pretty much like you, I break down my gun after every trip and give it a real good cleaning. In fact one of the reasons I stopped using doubles for waterfowl is that it was a real pain to pull the stock every time. One of the things I've found to help prevent rust is using WD-40. Now, I know that the stuff is not good for guns, but it works well if you do it right. First I break the gun down into component sub assemblies, including removing the bolt. Then I spray the parts with a liberal application of WD-40 and let it sit for a couple of minutes. Then, I wipe as much of it off as I can get to. Next, a liberal application of Break Free CLP or Rusty Duck will get rid of the remaining WD-40 and start the cleaning process. Last, if you prefer, you can use some RemOil on the outside surfaces of the gun as additional pretection against rust.
Like Slack, I don't think that it really needs all that attention. But it sure doesn't hurt, and it does extend the time that the guns are in my hands!