Using a high-volume schedule for many months is not the best tactic. Build speed and skill several months out, and then transition to a high-volume IM plan.
This program is a beginner plan to bridge you from an a Half Ironman to Ironman using a HRM with the confidence that you can complete the race without difficulty.
The schedule consists of 3 workouts per week in each sport, 2 days of strength training and core work too. The maximum volume is around 7 hours toward the end of the 12 weeks.