So: not unexpected though a bit faster when compared to wear and tear that happened to Spirit and Opportunity.
The good news is that a better choice of terrain can substantially prolong expected wheel lifetime. [Project Manager Jim] Erickson told me that they tested wheels on a wide variety of terrains, and came up with the following lifetimes. Keep in mind that these are conservative estimates, because there were no rover drivers working to steer around pointy rocks -- this assumes blind driving over all the worst rocks.
• Bedrock with lots of rocks: ~8 kilometers
• Lots of rocks, not on bedrock: 13-14 kilometers
• Bedrock with few rocks (think flagstones): 30-40 kilometers or more
• Smooth or sandy, with few or no rocks: indeterminate (causes no damage)