Those OEM drums are spendy, but they do at least come complete. Drum, ABS ring, studs, bearing. Many aftermarket drums come bare. Replacement drums shouldn't ever be necessary unless you let them go metal-to-metal, as both the OP and I did.
The problem is there are no 'squealer clips' on the rear shoes to let you know when they are close to gone. You gotta remember to check 'em every so often. Once they start making noise it's too late.