Some contributors to the list recommend freezing capped drone foundation
four or five times during the course of a season.  For a deep body hive,
this seems like a significant investment of hive time and energy, but I
assume offset by decrease Varroa infestation.  Is the 90% reduction really
observed?

The method for freezing is to simply take capped brood, freeze it
overnight, and then give it right back to the bees to clean out and prepare
for the next freezing?