I too think it takes more than a year to be competent to wade through a group and not cause injury. I'm not too sure it's a 20 year deal though.
My point earlier about pain, though poorly worded, was that if you train to cause pain, rather than the more difficult practice of finding, and leading your partner's center, you are more likely to believe that you'll cause your opponent pain and make an attack stop. This isn't always, and I think in the context of a serious fight, virtually never effective. If the training is to weaken the partners structure by leading them away from their own center, there is better chance of sucess, both at surviving, as well as at pinning the opponent without causing them injury.
Whether or not this is going to be always possible is, I think, a different thing than whether or not it is possible in a general sense.
Please God, don't let this one piss anyone off!!