The following graph shows temperatures for a month in an industrial kitchen. One can clearly see activities during regular work days and lack of activity in weekends.
The freezer has a strange trace. It starts out OK, but soon it stops to reach its minimum. A random manual daily check would probably had missed the malfunction but this automatic more frequent measurement shows the problem very clearly. In this case the freezer was missing liquid and after refill it worked well. This real life example shows how easy it is to detect disturbances in the temperature rithm just by eyeballing.
Read more about the PiGuard 2000 temperature monitoring system.