I regularly feed several hundred mice at a time and thawing them out takes a couple hours at room temp max. I somewhat find the the "we only feed live to our animals b/c our collection is so large" as a excuse. 90% of my customers demand snakes be on f/t and I make sure they are before I sell them.
Frozen is the only way to go if the animal will eat it. Also if you have a few that won't eat f/t offer a quail chick and they will rarely refuse that, even if they show no interest in f/t mice at all.