I have customers that ride WOT at all times - they're young and are saving so much money on gas that they can afford a new motor 2 or 3 times a year. Others ride in the 'sweet spot' of little vibration & noise (about 2/3 throttle) and run the same motor for years.
When going down hills or long grades its very easy to over rev during this time. Put a bicycle computer on your bike at least you'll know what speed you're traveling at. I use a tachometer on my bike as well. You can get one at Northern Tools for around $50. Then you'll know exactly how many rpm your engine is turning.