That's interesting. I have never broken an extractor on an AR, and I have been shooting them in one form or another for 25+ years.
You may want to double check operation. An overgassed AR will try to extract early, and put an increased amount of stress on the extractor. The could be remedied with an adjustable gas block, BRT gas tube that has a reduced port, or increasing buffer weight.
At one time, pistol sights were probably the most troublesome issue that I had. They went out of adjustment, fell off, or they mechanisms fell apart. Switching to quality fixed sights has solved those issues.