Honda Element 2006 O2 SENSORS

I have a 2006 Honda Element. Last year, check engine light test showed bad O2 sensor(s). I ordered parts and replaced. About 6 months later, check engine light - again, refers to O2 sensor. So I asked a mechanic about it - why are they going bad??

He said that 99% of the time, Honda Element owners are sold the wrong sensors. I cannot recall which one of the two, but he said one of them is usually wrong! I am wondering if this is accurate and I installed the wrong one - guy said this happens a lot??

He said the one that is usually wrong (I am thinking the downstream, but not certain) - costs about $100 more than the one that people are typically sold.

This mechanic has moved and I just want to make sure I order the correct sensors!!! Apparently - when you enter correct info about your Honda - one of the sensors is most often wrong. Can anyone help?? :))))))

Thank you in advance, Jenni