Like the title says...
found a few resources online refering to 15k miles to 25k miles.
...others say 100k miles.

 

I would do it in the middle, 50k.

 

Inspect them for wear & tear. If they look pretty much brand new why bother changing? Now if there are cracks in the cap and the rotor look like its fried thats a different story. I usually inspect them every 25-30k.