A cookie is such a transient data source. Some people regularly purge them all. Some people use more than one device. I wouldn't bother changing any preference

A cookie is such a transient data source. Some people regularly purge them all. Some people use more than one device. I wouldn't bother changing any preferences that disappear every time I clear out my cookies. For starters, I'd have to figure out where on the website the preferences are set -- and if it's in the user profile, well, just save my preferences there.