Brake pads - Should front and rear be the same?

So I am replacing the rear rotors and pads. I bought a kit and ceramic pads are included. My question is, should I keep semi-metallic to match the front OEM pads or will it matter if the rear pads are ceramic?
I have always replaced front and rear at same time, however fronts are in very good condition.

 

I don't think it matters. When I replaced my fronts my rears looked borderline new. I ended up replacing them all because I bought four but ill know for next time to check wear first.

 

thanks, appreciate the replies...I'll just stick with what is in the kit and use the ceramics.

 

I would keep the same type pad material front and rear. That would keep the proportioning front to rear the same as OEM, so as not to lock up one or the other prematurely. JMHO.