how many miles before to change the brake disc rotors?

I'd say that it's based on thickness measurement. Also, warpage (distortion) would be a factor. Don't believe it holds to any particular mileage number.

Cheers, Hank

 

Depends how you brake.Mine are above minimum thickness and not warped at 100K.

 

At 70K miles mine were badly grooved and were turned down to minimum spec showing just a tiny section of one groove. Totally usable for another ?? miles. I chose to go with new rotors instead of using the min thickness rotors.

So like others said, depending on use it's somewhere between cracking them on a race track and infinity. Depends on the user. I expect the rotors that I just put on to last the lifetime of the car. Just don't let the pads get too low.

 

And my pads haven't been changed in the last 70K... The booster needed replacing about 5 years ago.

 

Mine have recently been changed as the pads look almost new and I show 70k kilometres not miles.
Still got original rotors