Do you suppose it would be a cost saving idea by putting a chest deep freezer on a timer & turning it off each day for a few hours?

Normally, the compressor doesn't run continuously in a freezer.

There might not be any advantage to doing so---I don't know.

Safety probably involves the therman inertia of the contentws of the freezer.

Um... No that would defeat it's purpose and actually increase energy consumption.

The temperature in a freezer (and even a refrigerator) is controlled by a thermostat .. Unplugging the unit will cause the temperature to rise well above the set temperature .. And when it gets turned back on it will have to work extra hard to get back to it's set temperature .. Thus using up more electricity to run the compressor. Regularly unplugging it will increase your hydro consumption, not to mention increase risk of forgetting to plug it back in, allowing the temperature to increase to an unsafe level and allowing food to spoil causing you to have to actually discard most of it.  An expensive habit to get into .. not to mention a very counter productive one.

Having a unit that is in good condition and better yet is a newer energy efficient model is the only way to optimize energy consumption.  Don't open it unless absolutely necessary and if you do have to open it to get something out, do so as quickly as possible so you don't allow the cold air to escape and cause the thermostat to kick in to work to normalize the temperature. Don't over pack it.