My refrigerator/top freezer cools fine.
Freezer hits -5 degrees.
Problem is that when the cooling cycle stops, the defrost, or non-cooling cycle seem to take too long and allows the temperature in the freezer to go to 35~40 degrees.
Food partially thaws, then freezes again resulting in freezer burn.
Is there anything that I can do to -shorten- the amount of time spent in the defrosting/non-cooling cycle?
I have diagnosed and fixed my refrigerator-freezer. I’ll post what I found in hope it helps someone else.
I replaced the defrost timer. I discovered two things -
The timer was running a little slow - probably the 25+ year old motor 
I disassembled the switch - contacts were really worn and not making a good contact, which allowed the defrost cycle to run -longer- than it was supposed to.
Did all the continuity checks and all looked fine.
Moral - if your ref/freezer is old and exhibits these symptoms, bite the bullet and buy a new timer.