RE: consitintaly peep site tube breaking!
Acid rain? Severe ozone??
Or are you just cutting the tubing off too short?
If the tubing really has to work at pulling your peep in line, you really need to make adjustments. The peep should be set to rotate to your eye to begin with, and the tubing shouldn't be anything other than insurance.
Of course, if you set the peep to rotate to your eye properly to begin with, you wouldn't need the tubing. And you'd pick up anywhere from 5-10 fps in arrow speed. And your bow would be quieter.