I have a number of athletes that are really serious about the hard long hours in the pool. I get if you are trying to podium and you have an uber fast bike and run and swim is dragging you down this makes sense. I am referring to a number of athletes with a mediocre bike, a mediocre run and an average swim as well. They are spending 1/3 of their time swimming more than 1/3 running and the remainder on the bike.
I am just going to send a small reminder, you start your swim at the beginning of your race, when you are rested. You will be in the water if you are an average swimmer approximately 40 minutes in a 70.3 you will be on the bike 3 hours and your run 2 hours, this is a good finish time in a 70.3 for someone who is not spending their life training for the event.
If you look at this split your swim makes up just over 11 percent of your total time. Your run is 35 percent of your time, and that leaves 54 percent for you bike. If you apply some logic and think specifics your training should mimic time commitment based on the importance of the sport for time.
Your swim sets could be a couple, a short hard, a technique swim and an endurance swim, for 1/2 your long swim time is still not that time consuming.
Your swim should be done when you are fresh, it takes good concentration to swim well, don't do junk miles, focus on form throughout your swim.
The Bike never happens fresh in the race, get used to a couple bikes post swim to get the legs ready for the transition to bike. Make sure your bike volume is up and you are getting some hills and intervals in on other days. The bike is something that is easier on the body, so overtraining is not as big of an issue. Don't forget to practice your pacing so that you are doing your run bricks right after and you are able to understand how hard you can push the bike without it costing you the run, use the long bike as a place to practice nutrition, it is here where you consume the most of your calories, you should train that way.
The run, always falls at the end, however you don't need to train it there all the time, you should think of putting your swim and bike ahead of the run during training when you are doing multiple workouts per day, the bike can be a good warm up for the legs before the run. The run should also have some hills and intervals as well as your long endurance run. As running produces the highest volume of injuries try to be careful building your run, no more than 10 percent per week increase on your overall volume and your long run. You should also be thinking about things such as running surface, do not expect to move from a winter of training on the treadmill to running outside for your long run on the first warm day, that increase in hardness of your running surface can leave you injured even if your volume built up slow, you need to think about the small things. New shoes are the same phase them in slowly so you are adjusting your body slowly to the new change. The run happens at the end and its success hinges on your doing your nutrition correct, your running gear correct and your bike pace, correct. Focus on your nutrition and bike pace during your training so you have the perfect race strategy come race day.
When your need is to learn how to swim that may outrank your bike volume if you are limited in time, so I understand when you need to know you will make the distance the time commitment to swimming increases it is the one part that is about being able to complete the remaining part of your triathlon. If your swim is a good time, then think about picking up your bike more often, the more successful you are at getting your bike speed up and also having the recovery you need to then do your run right after requires really good endurance on the bike. Run volume should be related to the distance you are running, the longer your run the more limited your excess running becomes, running a Marathon doesn't require over distance training, whereas you can get away with that on the bike and swim. Running still poses the many dangers of overtraining injuries.
Be smart this year, write out meaningful goals and look for times that are equally ranked across, the more even your split placing the higher your overall placing will probably be.