As of now, I use the one tail every two week rule. Back when I was originally the Six Tails Jinchuuriki, several years ago, that was the basic method that everyone was using. And I thought it was still the same one to this day.
I never heard of One Tails every Seven Days. But I heard of the KG stacking thing which, I thought, was voided over a year ago when I was the Eight Tails host on Hazama because I attempted to use it and got scolded and was told to use the one tail every two weeks rule.
As for what Eric mentions, about RPing to get your tails, I also took part in that, as well, when I was the Eight Tails Jinck. I also thought we scrapped that method because, technically, the person could do a page or two long RP every day for however many tails they have and BAM! Right after getting the Bijuu they now are a master! Especially if you get help from another Jinck, that is basically an automatic tail right there.
I've been tossed around so much with the rules I've gotten sea-sick. I think RP should be implemented into getting the tails, seeing as anyone can just sit around and claim them, but I think there should be stipulations and rules set on it. Or, hell, maybe even a choice between sitting around and waiting or RPing it out because, well, why not?