It takes up to 10 years just to get enough of the basics down, especially in regards to the accupoint system, in order to be a level 1 instructor. Why ten years? Apart from understanding what you are trying to do, the length of time it would take someone to learn any skill would depend on how dedicated they are. I heard some Tai Chi teachers claiming one cannot possibly learn Tai Chi for self defence until they have been doing the form and puch hands for a number of years. And I am talking about self defence applications not some B/S moving without touching tosh. Not certain how someone who has practiced and is practising untold numbers of differing martial arts is in a position to know anyway. Tai Chi is a complex and fascinating art which demands full time devotion to it not just a bit of this and a bit of that.