Load banks are used extensively for shore side industrial diesel generators, and many companies only do it annually to verify the system can handle all of the life safety loads in the event of a power failure. If they don’t have one integral to the system, a truck can bring one in for a day. I have never heard of one for a boat. I am late to the party, but seems the answers previously given make sense. Load it up as best we can, but not sweat it.