My altitude experience is rather limited, but here goes.
Last year I was mostly untrained, my exercising was limited to actual hiking. I had several hikes starting at 10,000 and ultimately culminating in a successful day-hike to 14,000 and back. I was super-slow even at 10-11k. Above 13k I'd get seriously out of breath, I'd have to stop and rest after every 50 paces. But I didn't have any symptoms of AMS.
This year I've been averaging 8-10 hours/week of cardio (biking), a lot of it in high heart rate zones, at 140-160 bpm (I'm 31). I had one high altitude hike, Whitney main trail, which took just under 7 hours one way. http://app.strava.com/hikes/11172273 I think I've gotten considerably faster compared with last year. I was getting a headache toward the end of the climb, it could have been early stages of AMS or it could have been an excessively tight hat, not sure. 2x tylenol took care of it, I got to the summit and back, I didn't see any of the more advanced symptoms.
I live basically at sea level (700 ft).
