It's a ceramic disc. Since there is no wind erosion, if it doesn't get direct hit, it should last quite some time. Footprints from first landing are still there

It's a ceramic disc. Since there is no wind erosion, if it doesn't get direct hit, it should last quite some time. Footprints from first landing are still there - and are expected to be for at least next 10 million years - so you can expect finely-engraved piece of rock to last much longer.