mmm, we've been doing foundationless deeps for 6+ years and never wired them. i'd estimate 1000 or so frames in the field?
i've had, i think, 1 "comb failure". the trick is how you handle the frames. instead of "grabbing" them, i tend to rest the top bar ears on my fingers so that the frame balances itself. i'm not sure how to describe the "turning the frame over", but you keep the comb perpendicular to the ground.
the biggest problem was training the bee inspector :)