How close to set temperature is reasonable for a fridge freezer?

Since acquiring thermometers for my fridge-freezer I have noticed the temperature goes up and down for quite a bit. Sometimes it seems to get too warm before the thermostat (or equivalent in a modern fridge-freezer) kicks in and the compressor fires up and starts cooling. Is the any published guidance anywhere as... show more Since acquiring thermometers for my fridge-freezer I have noticed the temperature goes up and down for quite a bit. Sometimes it seems to get too warm before the thermostat (or equivalent in a modern fridge-freezer) kicks in and the compressor fires up and starts cooling.

Is the any published guidance anywhere as to as to what temperature excursions are reasonable and beyond which represents a dangerous defect?

And at what duration is an automatic defrost cycle too long so as to become unhealthful?
Update: Thanks for the response Tony. But I still don't know what temperature range of variation is reasonable and what is too much to be reasonable. Anyone know a source of information on this?
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