There is no written rule on when to make the switch (if ever). There are, however, a few factors to consider:
Cultural preferences and expectations
- Your own
- Your advisor’s
- Your university’s
Past email signings
- How your advisor addresses you
- How your advisor signs their own emails
Relationship to your advisor
- Does your professor have a preference on how they are addressed with colleagues who have known them for a long time?
- Do you feel comfortable lessening the formality?
In addition to these factors, there are other ways that you might transition your level of formality. For example, I address professors and faculty with varying levels of formality according to their preferences, my preferences, and my relationship to them. I use all of these on a regular basis with different professors:
- Dear Dr. LastName
- Hi Prof. LastName
- Dear FirstName
- Hi FirstName