Originally Posted by copescobra
I just figure I must need them, think I've travelled almost 30,000 miles on existing ones
and don't know when prior owner actually put them on.
Copescobra: Generally all automotive disk brakes have a wear indicator.
The typical low tech "indicator" is a small metal tab on one of the pads that will rub on the rotor when the friction material gets thin. This makes an annoying screeching/scraping sound that let's you know it's about time for a brake job before the friction material is completely gone. The little metal tab rubbing on the pad won't damage the disks, it just makes noise, and sounds bad enough that your average joe knows that something's up.
The higher tech/modern way is a conductive metal indicator buried in the pad friction material that has a wire that's connected to a light in the instrument cluster. When the pad wears thin enough to allow the metal slug to contact the disk it completes a circuit and illuminates a light on the dash. Again this is designed to happen before the pad friction material is completely gone.
......so if your brakes are functioning fine and you don't hear any scraping/screeching noises, you have some life left.