Whenever plugging in a RV to shorepower, use the breaker to turn off or on. That prevents most arcing. A worn outlet can cause problems so if yours shows burn marks, replace it.
Running the engine without exercising the rig on the road is often considered worse than just letting it sit without starting the engine. In future, just disconnect the negative leads from the battery banks after fully charging them with 20 minutes on the road. Batteries will easily overwinter without being charged continuously as long as they're in good condition...if they're disconnected. They do need to be charged in the spring before use though.
After disconnecting the batteries: If you are connecting to shore power to keep something powered in the RV over the winter, like the refer (recommended), or a small heater to keep moisture at bay, just run power to that item not the coach because converters aren't suppose to be run without a battery load. Check your manual though, as some can be without problem.