A fan will help provide a more evenly distributed temperature so you don't have temperature layering inside the freezer. It will also help prevent mold. But it's not going to drastically change how much your freezer runs.
Are you using an STC-1000 as your temp controller? What is the F2 setting set on? That controls how much it will allow the temperature to fluctuate before it calls for cooling. I have mine set on .5 deg C, but since you're in Fahrenheit, I would set it at 1 deg F to lengthen the time the compressor is not running.
How do you have your temp probe placed in the freezer? Is it open air or in a liquid? I have mine in a half gallon plastic milk jug full of water. It reduces the reaction time to slight temperature fluctuations inside the freezer.
If I had to guess, my freezer runs once every 1-1/2 to 2 hrs.
I hope that helps.