Wow, I had no idea WD40 was such a hot topic. I use it to clean before lube when at home, and on the trail I use it to clean along with a toothbrush. Idea is to remove the dust/grit from the O rings and not meant as a lube. Keeping the O rings pliant and grit free will greatly extend the chains life.
By routine, I mean whenever it has been exposed to large amounts of dust or muddy areas. Don't know about y'all, but I carry a small can of WD on the trail, use it for tire changes, chain maintenance, and non stick cooking spray