Your approach is actually the ideal way to do it. If you consistently have the results you're looking for at a couple of pubs, why sleep around?

Always publishing in the same one or two places can save you a lot of time and help to make sure you have a receptive editor and audience. I'd do what you're doing if Medium had a large multifocal publication that would give a good home to everything I write, whether it's about books, politics, sports, or life in general. But, alas, it doesn't seem to exist.