Squeaky plastic hubcap

My prius C is only about two years old and the front left plastic hubcap has begun to squeak in such a way that people on the street turn their heads and look at my vehicle.
I took it to the dealer and the service manager said that this is simply a matter of the hubcaps aging and it is to be expected
This seems like a cop-out ... Does anyone here know if these should be covered under the warranty such that I should get replacements for free?

 

I took it off, and it squeaked no longer. Not once. I should try putting it back on perhaps after I clean it.