Tombstones That Last?

Reality Master 101 asks: "Being an engineer, I've always been annoyed by the quality of the average tombstone. The typical marble kind only seem to last a maximum few hundred years before the lettering gets worn away. Old-school stone ones were better, but you still max out at about 500 years. This started me asking the question of what would I make one out of that would last 1000 years? 10,000 years? Clearly a solid gold or silver tombstone would last without corroding, but that would be uneconomical and would probably be stolen. What material would give the most bang for the buck for lasting power? What other factors come into play when you start talking Egyption timespans? I was also thinking that I should mount the tombstone to the casket so it doesn't fall over or otherwise wander away." It's odd the links to things that you can find over the internet, so when I read this question, I was reminded of one of Piro's recent rants on MegaTokyo that starts off with an odd discussion about this very issue. Might the information passed in the beginning of the rant be a reason why tombstones made today don't last very long? Do Tombstones need to last for over 500 years, anyways?