my CPO X5 needs new brake pads only 5mo/4000 miles after purchase

[BoilerUp]

Hey everyone, I picked up a new to me 2012 X5 this past summer. The car had 38000 miles on it and was a CPO. I'm at about 42000 miles (the vast majority of the miles I've put on it have been highway) and just got a low brake pad thickness warning light the other day.

My understanding is that a CPO'd car would have things like pads, tires, etc. replaced if they were that low. Should I expect the dealer I bought it from to pay for the new pads, or did I just get unlucky with the brake pad wear?

Thanks for any help!