Re: groups opening up
Clean, don't clean, it's up to you.
My newest guns are at least 5 years old. I clean upon returning home, a very basic, simple technique involving Outer's foam and patching, followed up by a light coat of gun oil.
My guns seldom get dirty enough for accuracy to degrade due to fouling, but that's got very litte to do with why I clean. I have a fair number of them, and some may go a year or two between firings, while others may get fired several times a week.
I clean to eliminate fouling that sits, for an indefinite time, absorbing atmospheric moisture and slowly etching pits into the bore. With a borescope, you can tell my guns get shot, and that the fouling gets removed, but you probably can't tell how old they are, because pitting is usually limited to what occured before I acquired the firearm.
if you're not going to clean a firearm, and you're not certain it'll get fired again in the next two weeks or so, at least put down a coat of oil to serve as an oxygen/moisture barrier, preventing the kind of bimetallic/electrolytic corrosion that causes pitting.
My .22LR's are a completely different story. I seldom clean them. The bullet lube can often cover a multitude of sins, with uncleanliness being one of the most obvious.
Greg