This is my Ma and Pa's chest freezer from ages past. For around 20 years, it has managed to keep a temperature of around -18ºC. When they went on holiday, my mum would call and tell me to open it for around 5 minutes per day, as it got a bit excited and sunk to -30ºC if it wasn't given attention.
Recently, the temperamental temperature device within it finally gave up the goats, and the freezer went a bit mental, freezing as hard as it could, like a sub-zero electronic Spartan. Rather than paying for costly repairs, or even more costly total replacement, my father instead decided to monitor the temperature, and plot a graph to work out how long it needs to be switched on in order to maintain -18ºC. Turns out its around 23 minutes on, and then 23 minutes off each hour.
Armed with this knowledge, the next stage is acquiring a time switch that can be plugged into the mains.
And the atmosphere is restored.