Rear brake rotor replacement

[paul@longarmquilts.com]

I just finished putting new rotors on the rear end of my F350 SD DRW.
they only had 6000 mi on since last change. Both had runout in excess of .010.
Pads only had a small amt of wear. The truck sits for weeks at a time between use, Buffalo, NY weather. Is there something I should be doing, watching for to prevent reoccurance.

All thoughts appreciated.