1999 Escort ZX2 timing belts.

We had a belt go out at 77,000 mi.  It was at freeway speeds and by
the time we got off the freeway, the engine was shattered.  I had it
professionaly rebuilt, by a shop I had used numerous times over the
years.  After 20,000, miles there was belt trouble again, and the
valve regulator ???, was fixed, by Ford,  for $1700.  17,000 mi later,
the belt  idler bracket broke off, the front of the motor, $1300.
Yesterday ( 12,600 mi.later) the belt popped off.  I'm having it towed
in today to analyze.  This vehicle, since day one has been my wife's
commuter.  She goes 58 miles a day 5 days a week on the freeway.
That's pretty much it.  We live at 100 feet above sea level, and her
job is at 1700 foot level.  I had one guy tell me it was cause of the
climb everyday.
Also, this car has never idled smoothly.  I was told that that was due
to the dual overhead cam?  I have stopped and asked other ZX2 owners,
and they say the same thing.  One lady said her husband was a mechanic
at a Ford dealer, and he could not smooth out her ZX2?