The first step is to set goals for next season. Many athletes, especially ones coming off racing Ironmans, find it difficult to find their motivation to continue to train. It is important to take some time off, but one needs to be careful as two weeks off can become one month, then 2 months, and then 4 and the longer one takes off, the longer it will take to get your fitness back. By having goals it will allow you to map out your training plan and give purpose to your workouts.
Whatever your goal race, determine how many weeks will be needed for a specific build to that race. It maybe a 12, 16, 20, or 24 week build. Count backwards and determine when the build will start. If its a late season race, you may find the build starts in May or June.
With your build to your goal race figured out, you can now plan the off season. There are many ways this can be approached. If your build does not start till May or June, there maybe a spring race you can peak for. Or perhaps a spring half marathon so can improve your run. Cyclocross is another option. Not only will you improve your biking, but you will also improve upon your bike handling skills. The Illinois Masters swimming state meet is in April every year. Work on improving your time in the 500 and 1650 free and watch how it improves your swim in a triathlon.
Regardless if you plan to do a spring race or not, its is important to take some time off. Normally we will require athletes to take 2 weeks completely off before moving into a couple weeks of light training with little structure. This allows not only the body to heal, but the mind to rest as well.
Its a good time to work on getting rid of any nagging injuries or pains. You may need to do physical therapy. Take the time to get completely healthy. Build in strength training. It will be important to build up the body so it will be able to handle the strain you will put on it.
If you find getting in the pool, biking, or running is a little to much, find something else you like to enjoy. If you like to kayak, get it in while it is still warm enough out. Perhaps you always wanted to snow shoe or do more down hill skiing. Perhaps you were an ice hockey player at one time or a soccer player. Find a hockey or indoor soccer league. It does not matter what you do as long as you stay active.
Finally, now is a good time to spend time with family and friends. Training can take up a lot of your time. use extra time you currently have to spend it with those who support you.