how long do brake disks last?

That would depend on how often you use your brakes

they're right, it depends on which you use (front or back) more and how low your pads get before you replace them, a good way to check is to rub the surface of the rotors with your fingers, there shouldn't be any signifigant grooves, and they should be fairly thick, somewhere around 1/16 - 1/8 of an inch at least.

Replacing them is relatively easy and they're not super expensive, although they are kind of riddiculous, as long as you take care of brake maintainence immediatley when it needs it the rotors should last the life of the bike, or pretty damn close to it.

I'm about to throw a new rotor/pads on the rear of mine, it doesn't look too hard to me.

in case you modify your pads earlier they placed on down sure this may end them detrimental the disc. in case you're taking the wheel off your motor vehicle and run your finger from the interior the disc to the outdoors of the disc and sense no rdieg on the periphery then your disc is okay. If there's a ridge on the periphery of the disc you want to question this. in case you at the on the spot are not that well-known your self with brake platforms maximum garages do a free brake inspection, they're going to be able to inform you in case you require new discs. A disc is often warped, you would in many circumstances observe this by skill of a chuffing noise even as making use of alongside, braking or a moderate wabble on your steerage less than braking. wish this facilitates

This depends a lot on your riding style.

If you ride with a great deal of anticipation, use engine braking and rarely brake hard, they will last a long time.

I have a 12 year old bike (Yamaha XJ900s), 71K miles, pads last an average of 16K miles, still on first set of discs.

it depends on the quality of the brake pad also upon usage..