How long food lasts in a fridge will also depend on your climate, cooling speed (as mentioned elsewhere), fridge cleanliness, and how much you use your fridge.

Keeping everything covered with lids/clingfilm and/or everything vegetarian/vegan will also prolong fridge life. Keeping out ethylene (bananas, apples) from your fridge also helps.

I just had a soup batch in a few covered jars stay good for 9 days. In summertime things sometimes go bad in a single day.

The best measure is your own senses, if the food smells or looks bad, it probably is. And even then you can sometimes recook it (wilted vegetables can often be used in soup, stew, or even pie), especially if you catch it early.

Also here’s a neat summary with some other tips and tricks.