IMO riding at near HR max for the entire ride means that your body/cardio is out of shape. As you get more miles under your belt, and get fit you should see the HR drop down considerably. You also need to learn to breath properly that won't elevate the HR. The biggest problem with riding w/ the HR for so long, so high is that your body is near it's ceiling and hard to go fast/harder without hitting the wall hard. Recovery is also harder after hitting the wall.
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Rule #10 // It never gets easier, you just go faster.