Most of my sea life I worked on oilfield service vessels, which were chartered to oil companies or oilfield service contractors. The policies of these companies were to conduct fire, man overboard, and abandon ship drills monthly.
SOLAS requires that boat drills be conducted any time that 25% or more of the crew has been replaced. On these types of ships changes of crew and charterer’s personnel on board were quite frequent.
I never served in any Navy. Do they, to your knowledge, require drills at any set frequency?
I don’t know about any required frequency but, given that it was the Navy, there certainly would have been one. :=) Captains could exceed any minimum requirement at their own discretion and I’m sure that many of them did. As an enlisted man, I was just a participant.