I don't think it's THAT far fetched. I am not saying it's right, just not hard to believe... especially since the guy said most of the plugs were bad- he was probably just not in tune (no pun intended) with how his engine was running. So technically all the plugs didn't last that long, just enough to keep him running
I did mine at 120k just because but the plugs honestly looked like new. Perfect color, perfect gap, you had to look very close to see any rounding on the electrode. I know that is close to half of what he did did but I now have 208k and honestly believe that if I hadn't changed them, they would still not be causing problems (yet!). They were gm (probably delco) iridium plugs and I replaced them with delco iridium plugs and bosch wires.
I drive almost all highway and rarely less than 40 miles at a time. The gas is always fresh and 95% of it is from the bp by my house. I think with proper combustion and good ignition control plugs should last a long time.