I think a lot depends on where you start before going up to 14K. I live at about 7K above sea level, so going to the top of Pikes Peak (14,110 feet MSL) never seems to bother me. However, that's no sure thing because I've known people who lived here for years who get altitude sickness up in the mountain passes.

When we moved here almost 18 years ago, it took a long time to adjust to the altitude*. I came here straight from Officer Training School (then held in San Antonio) where I was running 5 miles every day. The first time I tried to run here, I thought I was going to have a heart attack. Even walking up a flight of stairs would leave me short winded and I had a headache for days. Aspirin helped with the headaches and eventually my body compensated by producing more red blood cells and greater lung capacity. It took time for all of this to happen. Now, when I go back to sea level, I have to remind myself to breathe every now and then just to keep in practice. It's why the Olympic Training Center is located here, too.

Every year when the Air Force Academy graduation takes place, there are several cases of altitude sickness from visiting relatives, especially the older ones. A few years ago, a 2nd year cadet actually died from an extreme form of altitude sickness. It isn't something to take lightly.

If you're going home back near sea level every night, then your body has a harder time adjusting to the altitude because the acclimations happen slower. It might help to spend as much time at higher altitudes as you can so your body has more time to adjust.

* The adjustments were to more than just our bodies. We had to adjust how we cook, too. Just about all baking requires adjustments for the altitude. Water boils at a lower temperature here, so it takes longer to cook a lot of foods. I know people who live near Woodland Park (~8,000 feet MSL) or Divide (~9,000 feet MSL) who cook pasta in pressure cookers. Simply boiling the noodles in a pan takes about 30 minutes and the noodles don't come out very good.