Did you realize that you posted your question in Summit County, Ohio? I am from Colorado, and I happened to be looking for information on this website.
I grew up in Denver at 6000 feet and I always enjoyed (and still do) going higher. With regard to the thin air, people generally adapt. You noticed that you are already adapting to high altitude after one week. Adaptation to high altitude has been studied a lot and as long as your cardiovascular system is in okay condition, you'll just develop more red blood cells and breathe a little more. And at 9000 feet, the air is so lovely to breathe!
I think the main problem with altitude is that the humidity is low. That thin air just can't hold as much water. You have to drink a lot of water and your skin will tend to dry up. If you don't manage to keep hydrated (my problem is at night) you can dry out your mucous membranes. So the challenge is in just staying wet enough. This can make respiratory infections harder to fight.
But there are pluses to dry air. My wife used to have sinus headaches when she lived in a humid area, and when she moved to Colorado her headaches went away.
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