Oil the chain when it's been in the rain, or shows rust, or when it squeaks. Be aware that younger people hear the squeaks sooner than older folks -- I drove my daughter nuts one day when she heard it as we started off, but I didn't hear it until late in the afternoon!
Do keep it clean, at least wipe-down clean. It's possible to just add oil, and never wipe off the excess, and build up greasy crud such that it never squeaks, and there's no bare metal, but the crud gets in the chain, causes a stiff link, and if you're lucky the chain breaks instead of something else. Miles from home, of course.