Could placing hot food in the fridge (as opposed to letting it cool first), cause significant reduction in appliance lifetime
The answer, as mentioned by +MonkeyZeus, is here: https://cooking.stackexchange.com/a/29857 

It can be summarized as: 


  This is a myth left over from the days of iceboxes. Go to any official food safety resource online (including USDA, FDA, etc.), and you will find they are all in agreement: it's perfectly safe to put hot food in your refrigerator. In fact, unless you are using some more direct cooling method (like putting your food in an ice bath), waiting to refrigerate your food is often a health hazard.