Just to be sure, are you referring to a chest freezer or an upright freezer? Either one can be referred to as a "deep" freezer. If it is a chest freezer, I would agree with day_trippr.
I don't think it would have any effect on your beer if it does have a built in defrost cycle. The temps in the freezer would most likely not rise much above your set temperature. I can't imagine it would be too difficult or costly to disable the defrost function.
Just my two cents. Good luck.
Rocket Socks Brewery