It's a good idea to start them and run them. It helps charge the battery, and gets the oils circulated.
When you do though, you want to run it up to full operating temp. You want to vaporize any mositure that might have built up in the motor. You also want to get it hot enough that it is not making more moisture.
You know how you get water coming ff the exhaust on a cool morning when you first start your truck or car? That's a byproduct of the cumbustion process. Once the engine and exhaust are warm enough, you don't have all that water coming out. That's what you want to shoot for.
My Granpfather used to go through an exhuast system every couple of year on his '69 GMC 2500. He used a work truck most of the time. He used this truck around the ranch, and a trip to the store once a week(only about a mile). That 396-4bbl just did not warm up in that short trip. It left lots of moisture in the exhaust, and the exhaust would just rust out(before stainless exhaust became popular).
It's also good to drive them a bit, just so the ring gears in the diff's throw some oil around(as well as the rest of the gears).