My worst episodes (with psychosis) were manias with mixed features. Occasionally, I even had depression with mixed features.

The majority of my elevated episodes are more elated or with irritability (fury even) but mixed features arise for me when the episode really worsens, lasts a long time, stress becomes unbearable, and/or I am transitioning to the opposite pole.

I guess I didn't exactly answer how often. Not easy to answer. Maybe a lot, but not the majority of time. My first was clearly at about 16 years old. Dozen or more since then?