"I am having difficulty with putting to together my annual training plan for an Olympic triathlon as my first 'A' race which is 6 months away (late summer). What do I do to change my plan without the risk of overtraining or peaking too early. Do I just extend my 'preparation' period?"
Peaking for an A race (A=high priority) is very tricky no matter how many years or how much experience you have under your belt. Personally, I think peaking for an A race with so much training time between the start and finish makes it even trickier.
For starters, no matter where you are right now in your plan, you could add in a Sport Focus plan – 8 weeks of intense focus on your weakness. It’s much easier to maintain fitness than it is to regain it, so you could take the 8 weeks to work on your swim (for example) and still maintain bike and run fitness on 2-3 workouts per week.
Another option would be to schedule a half marathon on your plan. That would give you some focus and keep your run strong even through the winter months. There is nothing like having that carrot out there in front of you.
My recommendation on your plan would be the following:
Prep Period – 4 weeks
Base Period – 4 weeks
Single Sport Focus – 8 weeks
Base Period – 4 weeks
Build Period – 4 weeks
A-Race / Peak Period
= 6 months
If you have another A race after your first race, I would recommend two or three weeks of training, completely aerobic and nothing over a Zone 2 Heart Rate. You can swim, bike, run and lift as much as you want, and even go back to Base Period volume and but keep it easy and repeatable.
Following the 3 weeks of easy aerobic work, I would have a solid 6 week focus on building the volume and doing more race pace type workouts. It would look something like this: 3 weeks post race – easy volume
6 weeks of Build / Race Pace Period
2 weeks of Race / Peak Period
Many people will not want to take that break coming off a peak, but you can only sustain the real hard training for six to ten weeks (and the ten weeks is for athletes who have a lot of race experience and can hold form for a few weeks). For most of us humans, holding a peak for longer than a week is hard, so getting in that nice easy aerobic base is very important as it resets the body and gets it ready to hit it hard again! Good luck and have fun this season.