I used both Bosch and Walker O2 sensors back in the days before I started driving Volvos. I never had a Walker 02 sensor last MORE than 2 years (20,000 to 30,000 miles), and I've never had a Bosch 02 sensor last LESS than 5 years (good for 50,000 to 100,000 miles).

Personally, on my 240 and my 780, I use a Bosch 13913 three wire sensor and crimp the old pig tail on. My out of pocket cost is $40 for the sensor, and about $3 for the crimps and shrink tube. Do not ever solder the wires for an oxygen sensor, as it needs to "breathe" a tiny bit down the strands. The sensor probe has to have fresh air inside the sensor for it's reference base, and it slowly expires due to the chemical reaction that generates the voltage.

(my above experiences apply only to LH/Bosch fuel injection systems, and not to Bendix/Rex/Regina fuel injection systems)

God bless,
Fitz Fitzgerald.