April 26, 2016: Since the unrelated flat that I got in the front tire shook the original sensor loose from its attachment, I've been trying to test with a back tire with little success. Last night I had a moderate success that still ended in failure. The issue is that I have been testing flexible sensors for durability. Last night I put a flexible sensor in the original tube. Basically, the tube has a large hole in it as pictured in the gallery, and I put the flexible sensor over this hole and covered it with a large rubber patch as I had before. This effectively put the sensor inside the tube, and no longer was it pinched between the tube and tire. I figured this might help with the sensor cracking issue I was seeing previously.
I checked the sensor periodically, and it worked happily up to about 5 miles. Then the tire went flat. I wasn't that surprised because I hadn't been able to get the patch to seal properly. Unfortunately, the brief time I was riding on the flat tire without realizing it killed the sensor, so I won't know how long it would have lasted. It appears as though a single component on the back wore through the patch and created a pretty major leak.
I have one more flexible patch I can try - I think this time I would plan to cut a slit in the tube and try to adhere the patch to the inside of the tube and then patch over the slit. I would remove the single (and unnecessary) component from the back of the sensor so it wouldn't wear through. One issue I'd have to overcome is that tubes are coated on the inside with a powder that makes it hard to stick anything to it. It's there so the tube interior doesn't stick to itself.
Otherwise, I need to wait for the sensors I shipped to various Chinese tire companies to reach them. It's been over a month so far and none of my three shipments have made it. Maybe I shouldn't have tried to save money by shipping them without tracking!