New O2 sensors ?

[Mustang_289]

Just completed installing a complete MAC LT exhaust system. I need to extend the O2 sensor wires - I was planning on simply adding wire to the existing O2 sensors... My question is should I pickup a new set of O2 sensors? Do these things get old and tired and need replacing? These things cost about $60 and wanted to save the money and simply add some wire to extend the connector.