I've not seen JK's video, but from the description I've seen, it will be useful for a long time (well, unless you learn very fast!). According to somebody on another Mudcat thread recently, the pace is quite fast - "he doesn't take any proisoners" was the phrase used...
You couldn't have a better and more inspiring master of the instrument to follow though - I've learned more from watching and listening to JK than anyone else.

Don't be daunted by stuff about "frustrations" - it's common to all folk instruments that they have limitations. Learning how to get the maximum music with the fewest resources is what makes it fun.

Anahata