Bosch or Walker oxygen sensors

[Joshua R. Abel]

Has anyone ever had any problems with the Bosch or Walker Oxygen sensors? My car has been running pretty poorly for a while. When I did the check engine light routine, the code came up 02 sensor. So I swapped them out for some Walker sensors. They lasted about a week or 2 before the problem re-occured. I swapped them out for the Bosch and it didn't change anything.
I gave up on trying to fix the problem on my own, so I took it to the dealer. The technician said the code is still coming up- bad 02 sensor. So, I should just buy the Subaru 02 sensors @ $1,000,000 a piece, I'm sure, and this should fix the problem.
Any advice from anyone would be highly appreciated. And yes I already swapped out the spark plugs. So that probably isn't the cause.
Thanks in advance.