George, Actually I have 2 kinds of caps. The one’s with the pressure written on them and the other kind that adjusts to the pressure once installed and I have not had an air leak problem with either kind.
It could be that ridding in the boonies on your bike put to much strain on the cap where standard driving while pulling a camper would never go to that extreme.
It was stated in this thread that they loose air pressure and I have not found that to be a fact whereas you had a total catastrophic failure due to extreme use and that is a different issue. After reading of your problem, I too would not put them on a motorcycle or ATV.
One of the 2 manufactures at JCW.com state that should the top of their cap break off there will not be any loss of pressure however I do not remember which one stated that. It can be found out by going to the following link and researching the 2 brands on their respective home sites