Funny you should mention the lactate threshold, RoadRaven. I was just reading something about the recently, and it's something I had never really heard of. The line of thinking for years was the lactate builds up in your muscles and hinders performance. To counteract that, coaches would have athletes do exactly what you are describing, working just at the lactate threshold, to gradually increase the threshold over time. Science has finally caught up with sports and they find that lactate is actually used by the muscle for energy and the way coaches have been training athletes is the best method for training.

Sorry, I'm sorta a science geek and find this stuff really interesting. Just find it funny you should mention that.