Dear Randall
I took your advice, and in sense of preventative maintenance, I changed all 4 sensors, then odometer reached 52 miles 2 weeks ago.
After hours of my research of best price, I found
www.************************************************************ and bought 4 of the sensor with final price with taxes and free shipping $426.85. Then you also have to fill the rebate form, which gives your 10$ per each sensor back. So the final price is 96.5$ for the O.E. type 13806. Plus no problems with wiring, because to do that under the car is pretty difficult. Sensors themselves are very fragile; i was very scared to broke them. And you know Randall; your advice actually works, because the old ones were almost burn out. So thank you for advice.
Here is the rebate form for O2 Bosch sensors. I hope this will help you.
I am strongly suggest not to make a mess with wires under the non-comfortable space under the car and go with the O.E. type.
here is the link to 10$ rebate for each sensor
http://www.boschusa.com/AutoParts/Promotions/GasCard/