Re: On Koryu
Cliff - I really don't know the answer to that, personally. But, consider this: I have a student who can only train with me every six weeks or so. But he is getting very very powerful. Why? First of all, because he's a very strong martial artist already (see Toby above), and because whatever I teach him, he actually practices - a lot. For example, I showed him a method of doing proper body organization for every cut in Araki-ryu. When done properly, one is absolutely silent. If you do it wrong, your foot thumps (this is easy to do - doing it right is hard). So when he tucks his babies in to bed, he does 1/2 hour beside their bedside every night. If he wakes them up, he's doing it wrong.
I'm in Greece now, where I go twice a year to teach. I really had my doubts about this kind of long-distance study-group teaching, but my students in each ryu practice many times a week. They are getting the core information, so their progress is pretty good. To this extent: I'm making a video archive of the kata of Araki-ryu. I taught a set of new kata, and one man, in particular, over the course of four days (six hours a day) got good enough that I used him as tori in some of the filmed kata.
I've told the story before, but my instructor in Araki-ryu trained as the only student of a bunch of old men. Sometimes, he'd be off to the side, doing suburi, and one of the old guys would call out: "Hey, look at this." And they'd show a kata he'd never seen before, once, never show it again, and refuse to explain it. He'd go home and work on it, using his little brother as a crash test dummy. He got menkyo kaiden in eight years. (He went to their home every weekend.
So 5 - 7 years? How hungry are you? How attentive are you? How hard will you work?