I'm the anomaly among cast iron people. While I have an slightly embarrassingly large collection,a few quite old and slightly rare, I still wash with soap. I've actually got a good enough season on them so that I've had the wife leave one in the sink overnight full of soap and water with no oil effects. The only one that has that slight issue is the round griddle. All I can figure is the real high heat, repeatedly, burns the season off the bottom. Either way, of what you do works then keep doing it. That's how I've always felt when it comes to old ci, I certainly don't get as excited as some of the collectors about how they need to be handled