I picked up a new 1/2 barrel today and overnight I noticed only a drop of about 3 degrees, down to about 43.5F.
My usual cycle temp is between 28F and 34F, which is pretty cold for beer, but I like it that way.
I noticed my freezer plate is totally covered with frost to a thickness of about 1 inch, so I unplugged the fridge and left the freezer plate fan running to melt the frost.
I would expect better performance once it thaws.
This is something that should be done once the barrel is empty and removed since there will be some water drippage.
The, by the time you get a new barrel, it will be frost free.
Keep in mind, reducing the temp of a 1/2 barrel will take a few days to settle out.