Toyota Repair: minvan repairs, sienna minivan, brake caliper


Question
I have a 2000 Sienna minivan (100000 miles)that's gone thru brakes/rotors/calipers/wheel cylinders WAY more in the last 50K miles than I think it should have.

It has been serviced by the same local/convenient repair shop during this time. I'm beginning to have my doubts about this repair shop; their work, the parts they use etc etc.
Example: I had the front calipers/rotors/ pads etc replaced at 80K mile, 1 1/2 years ago.
Last week, hearing grinding noises again, I took it in, he said the calipers froze up, and everything needed replaced again! Is this normal?
Could he be using "cheap" parts knowing that they won't last? Are there different levels of quality in parts such as these?

(FYI: the brake pads & rotors have been replaced MUCH more often; just used the calipers as a glaring example)

I'm a reasonably conservative driver, don't ride the brakes, take  good care of maintenancing the car... I'm just concerned that I'm being had.

Or are the early Sienna minivans prone to this type of brake wear that I've experienced?

Your help is appreciated.  

Answer
The first thing I will recommend is stop going there, something just doesn't sound right, brake caliper problems on any toyota models are extremely rare and in the 30yrs time working on them I can't recall having to replace a caliper, THIS JUST DOESN'T SOUND RIGHT.
I'm going to recommend that you visit a toyota dealer and have them check the brakes and follow their recommendations and no, the early siennas are not prone to excessive brake wear, you should get at least 30,000 miles from the front pads.