Originally Posted by
MDcatV
the best racers i know are doing >20 up to 32 hrs./week. they're racing on trek/livestrong, radioshack, geox, cal giant, us armed forces, and a few who are older and racing on local teams. there's a reason they're successful beyond just being talented, and also a reason they're doing that volume. it benefits them, and they have the time/desire.
It bears repeating... especially because I think the OP is fairly new to the sport. There is no substitute for volume (and only volume) for a substantial part of your training cycle. I don't think anyone truly understands why, but it causes adaptations that improve aerobic endurance that will simply not occur otherwise. And every race you do depends on aerobic performance. Don't mix in some intervals or sprints because you will just screw it up. Just lay down the miles at a pace that you can sustain. The higher intensity performance takes far less time to max out, and you can work on that when you are building up to a peak.
It's almost like I got religion. I'm old, and I've been avoiding this for 25 years. You will see big and quick gains with high intensity training, but then you will plateau and go nowhere.