would be easier to buy intermediate and just add z2 time as you have it available. If you find that isn’t enough have them swap it out. This is what they told me the difference was between intermediate and advanced ( and you can also see how easy they are to work with). I agree with Bbarerra about a custom coaching plan. I was with them years ago and they are wonderful, it just isn’t in the budget right now. ( my youngest son is the one with the custom coaching plan now):
Hey Alex!
To answer your question, it is both an increase in total hours and in the length of the intervals. During the first 3-6 weeks of the plans the length of the intervals are pretty similar, but the weekend rides are longer and include more time in SS. As you progress, the intervals during the week in the advanced plan get harder too (e.g. 4x10 SS bursts in intermediate plan vs 5x10 SS bursts in the advanced plan). To help you get a better idea of the difference in the total hours, I am attaching a chart below.
