I'd suggest you read "the first 20 minutes". It's the most informative training book I've ever read. It's actually written by a runner but nearly all of it applies to cycling. While you need seat time to break in your butt, your aerobic conditioning and power will be best developed by HIIT (high intensity interval training) workouts. Hard workouts, 6 days a week, would be overtraining for many people and you can start recording your resting heart rate as one good indicator for when your body is stressed. Your muscles need a "break" to rebuild so it's a reasonable question to ask.