I've got an old .46 FX that I've been flying for six seasons now, and it was well used when I got it. I have a Magnum XLS .52A two-stroke that I've had for five seasons; it has hundreds of flights on it and it still has a nice, tight pinch and the top of the stroke.

Maybe you're running your engines too rich and your piston liners aren't getting hot enough to expand properly. That would explain any broken connecting rods and/or pins.