I would have hoped so, but I contacted NGK when their Ruthenium plugs came out, shortly after I did the plugs in the Kia.I think you may have some more leeway since around the states those go around 100k miles + +
They said 100,000 km (probably rounded up from 60,000 miles) for Iridium, and 120,000 km (c. 75,000 miles) for Ruthenium.
Agreed, those are probably conservative estimates.