When to replace front O2 sensors

[JimDavis MT 97GTS 650R]

My 97 GTS now has over 50,000 miles on the clock. I have two questions:
(1)Is there a prescribed mileage to change out O2 sensors with new ones.
(2)My front (up stream) sensors have extra long wires (a non stock item supplied by a former engine builder who shall remain nameless). Anyone got a clue where these little gems can be found? Thanks in advance....(JD).

 

[Ulysses]

I usually hear from mechanics that they should be changed out every 50K, but they are made to last ~70K.

 

[Larry Macedo]

Jim,

At the time, I was purchasing those lengthened O2's straight from NGK Japan to my dimensions. You will most likely need to lengthen the harness side of the connector now if your planning to replace the H>M>S O2's. I believe it's prescribed they are replaced @ 60K.

 

[JimDavis MT 97GTS 650R]

Thanks for the replys guys. Larry M, I would presume that "lengthening the harness side" would mean that I could splice the harness? Correct? (Just want to be sure I understand) Thanks. (JD)

 

[Mike Adams]

It is easier and cheaper to get a universal O2 sensor and replace it. They come with connectors and everything. Just cut the [******] O2 sensor and splice these in. They heat up quicker and cost next to nothing. I use Blue Streak part number SG300 or for factory plugs for front 02 I use Blue streak SG229

You can get any make of Universal 4 wire 02 sensor though