Is there anyway to tell that a spark plug needs replaced?

I've put about 10k miles on my car since finishing building it and having it tuned and have always swapped in a new set of plugs with every oil change at 2000 mile intervals. I've done this because that's what i was told by my tuner and also what i have read. I'm not complaining about the frequency or the cost, i was just curious if its actually necessary or if there's anyway to tell that they need changed besides watching the mileage? Is this common practice for the rest of you?

 

when they start breaking up at high rpms <

 

i think every 2k miles is excessive. i do it every other oil change and even that might be a bit much. i guess it really depends on how you drive and your tune. my car runs pretty rich at cold idle so im sure the plugs dont like that too much.

 

i do every other oil change as well and they allways look good...could probably go longer but ngk's are cheap!!

 

the copper core will start to lose conductivity around 5,000km.

if you pull the plug and some of the edges are rounded, time for new ones.

 

Thanks for the info. I think i might start doing them every other oil change. A lot of my miles are highway anyways.