We put them in the RV and leave the radio on. We let neighbours know if we will be gone for more than a couple hours. How long we leave them depends on the dog. 8 hours wasn't a problem for a young dog. 4 hours was a stretch for ours when they got old.
We NEVER close up the unit and put on the AC. If there is a power failure they could roast fairly quickly in hot enviroments. Instead we open a window at either end (ON THE SHADY SIDE) and set the fantastic fans to come on at 60 degrees celcius. Whatever the temperature outside is that's what the inside temperature will be inside plus or minus. Two fantastic fans will change out all the air in a 40 foot motorhome every 10 minutes or so. They are 12 volt so even if the power goes out they just keep running. If it gets much over a 100 we put them in a kennel if we have to leave them.