o2 sensor problem

My 96 showed code error for a bad sensor in bank 1. I replaced it, less than a month later the same problem has begun. Gas mileage dropped quickly and it idles rough.

What could cause an o2 sensor to go bad so quickly? Defective?
I have a slow leak in the power steering pump and appears that it has drip onto the sensor wires. Could this be the cause?

if the fluid from the leak was able to get inside the sensor body, or past the threads onto the "nose", it certainly would ruin the sensor.