bor1234 said:...Thoughts or experience???
Nothing wrong with BTR's approach, basically it's shades of gray you're talking about. You can baseline on FTP, 30 minute power, 20 minute power or other benchmarks and the workouts you describe are very similar to what the SST/Coggan/Lydiard folks advocate.
Remember Andy's second best way to estimate FTP is to track your regular, repeatable long interval power during training. IOW, it's not all that different than your regular 20 minute power. Sure the VO2 max definition changes a bit, but in practice you're going to do 3 to 5 minute efforts totalling near 25 minutes roughly as hard as you can manage and still complete the session. Pretty similar to what you describe.
I think there is a place for longer rides although I agree with the good Mr. Willett that it doesn't provide the most focused stress for mitochondrial growth. But it does bolster overall training load or CTL in powerspeak. I don't know that I agree that you have to train a certain number of KJ, but if you're gonna ride or race long events you at least need to get used to being in the saddle, feeding yourself, pacing for a long day, etc.
Anyway, his plans are sound and a good approach. Just one that uses a slightly different reference point but the training methods and the stress on metabolic fitness adaptations with near maximal 20 minute repeats and VO2 max work is pretty similar.
Good luck,
-Dave