I detail clean mine after every outing, sometimes blowing a whole rag-shirt's worth of patches in one session. I like mine squeaky clean and well-oiled (especially with the humidity in the air around here being an open invitation to a rust party), and I often have my friends help me do it. They don't have guns, and like to shoot mine, so they help me take them down once we're done for the evening.
I've been meaning to construct an electrolytic bore cleaner for quite a while now. Apparently it's supposed to be able to restore the bore of old war rifles like Mosin-Nagants to the sheen of a new barrel in some cases, by drawing out the years of uncleaned fouling, hardened cosmoline, and gun powder residue bonded to the surface of the metal.