Annual o2 sensor replacement

[kszygc]

Once a year or so I have to replace the downstream O2 sensors on a 99 Silverado. By that I mean the 2 sensors after the converter not the two before. It has the 5.3 w/ auto trans, auto 4x4. The previous owner cut the y-pipe and installed 2.25 inch pipe all the way to the rear without mufflers at all. I bolted on a pair of 4 inch supertrapps at the back end to cut down on my hearing loss, it's bad enough as it is. It has a K&N fitercharger kit and unknown brand of shorty headers. The computer is still stock though. I will get the DTC for low volst and no volts so I pull the sensor and it is in pieces internally. They aren't terribly expensive, I just get tired of replacing them. Anybody have any ideas or experience?