Ya, doing power like that after some KJs "in the bank" is good too since its race specific. Once or twice a season I'll do a workout where I bookend high z4 20' intervals around a race pace group ride, and hammer the ride. The "on" portion of the ride is only about 90 minutes, but man, that last 20' interval is real tough.
__________________
"Your beauty is an aeroplane;
so high, my heart cannot bear the strain." -A.C. Jobim, Triste