For 2022, my first A race is March 18, a local sprint triathlon. After that I am scheduled to do the Boston marathon (April 18) which I consider an A race also (with the goal being to run the whole way). It will be my 3rd marathon, my pb is 4:05, my Boston time goal is 4:20, I am 64/65 years old, my 5k pace is 7:12, I have 5 years of tri/run experience. How might I purchase a plan that would be customized for optimizing these 2 races?
That’s a tricky combination, because the two events are very different in nature yet close together. A custom plan would be optimal, but these are more costly. If you’re going to try to prepare for both events with off-the-shelf 80/20 plans, Your best move is probably to chose a sprint plan as your base plan and gradually lengthen the Zone 2 runs beyond the prescribed durations as you make your way through it. Then switch over to a marathon plan after the sprint, but replace two weekly Foundation Runs with easy swimming/cycling to avoid an abrupt jump in run frequency. Be sure to study your chosen marathon plan ahead of time to ensure you are prepared to transition over to it after completing your sprint.