Stimulate, don't annihilate
In triathlon from the beginner to the professional athlete we see time and time again that athletes annihilate themselves with too much volume or too much volume coupled with too much intensity. The reason is because that's all the athletes really see or get exposed too. You are told to start out slow and build that up to going long and then somehow after you have taught the body's muscles etc to fire at a certain rate for a long period of time then switch that closer to your big race with some speed work. The body just can't lay down a specific new pattern in a number of weeks.
I liken this high volume and long slow distance approach to that of the gym/fitness industries over-reliance of body split/part programs which may favor those training specifically for body building (or using steroids) and not physique and overall health.
The key to effective training is to do 'just enough' work to stimulate the training response we are after, then recover that system as quickly as possible so we can train it again effectively. When we want to improve anything in life we need to do it with a high frequency. If you're trying to improve your swimming then 4 sessions per week is ultimately better than 2-3 sessions per week even if you hit essentially the same total volume.
What is just enough? Well that depends a lot on you and your life circumstances such as job, family commitments, training background and how much time you realistically have. Your goals need to be congruent with these circumstances above. Wanting to train for 12 weeks on 12 hours a week and get to Kona just won't cut it. However, consistently training 12 hours per week over a long period of time with a bump up in volume for a number of weeks before your Ironman will give you an infinitely better and more realistic chance of qualifying for the big one.
When you train with the typical high volume approach you are not only forced to train with lower frequency but also lower quality because you're too tired to not only push when it counts but will miss sessions because your aerobically whacked. However when you train for a long period of time with proper training, you will have built up a significant amount of triathlon specific strength, speed and motor patterns and you'll start seeing some pretty impressive jumps in performance.
When you annihilate yourself with huge volumes it's two steps forward, two steps back but when you stimulate the systems with lower volume and higher frequency, it will take you one smaller step forward consistently, but remain there with no steps back.
Go ahead stimulate the systems frequently 'just enough' and annihilate only your competition.
Kristian