Re: Varroa mite lifespan
Here's one reference from University of Florida to varroa lifespan:
The UoF link above is a fairly comprehensive review of varroa lifecycle, and includes some great photos.
The phoretic period may last 4.5 to 11 days when brood is present in the hive or as long as five to six months during the winter when no brood is present in the hive. Consequently, female mites living when brood is present in the colony have an average life expectancy of 27 days, yet in the absence of brood, they may live for many months.
Clemson University has slightly different numbers:
USDA Zone 7A Elevation 1400 ft