What is a good rule of thumb to use large aperture for portraits vs showing more background?

I recently got a Canon 50mm and have found myself probably over-using the large apertures for portraits. I’m curious if anyone has a good rule of thumb for when to avoid it.

My sense is that its good to:

1. Really focus on only the subject
2. There are undesirable things in the background
3. The background may be far away (landscape)

Does this seem right? Any other suggestions?