i have started blindfolded two weeks ago, and i did 15 minutes too on the first time i solved it
i'm really not an expert, but i don't think stories is the best way to memorise : i simply remember the stickers, and as they often do some kind of patterns, by group of two or three, i now manage to learn a cube in three minutes. i prefer this method because inventing stories needs imagination, to get to a sort of code, and then you have to decode again, which is so long. by remembering directly the stickers, you can execute directly whithout having to decode the story you remembered. As i've said i'm not an expert, but i have droped my memorisation time from 5 minutes to 1min30, and i solved the cube in 6 minutes (and i did about 50 atempts only yet).
good luck !