I'm in the "use-by dates are only suggestions" camp. Especially for canned & hermetically sealed foods. I inherited a "waste no food" attitude from my parents who grew up in the Depression, so in my world it's a moral failure to throw food out. Which raises havoc when you're a one-person household, but also a fanboi of Costco and their mega size vittles. It's a constant race between me & the bacteria to see which of us is quicker at eating down any given dish's leftovers.
All that to say that I've eaten sealed yogurt that was more than a year out of date (it's just pre-soured milk anyway, right?), cut/scraped/scooped small mold colonies off solid/pasty/chunky foodstuffs & eaten the rest, consumed MRE's twenty years past due, dug in with breakfasty relish when I forgot last night's dinner leftovers on the counter, and I think on one occasion ate what must have been leftovers from a Roman Empire cavalryman's saddlebag. I didn't eat some 17 year out of date beef jerky only because it failed to reconstitute by soaking in water for several hours. Oh well, you lose every once in a while in spite of your efforts.
My approach to refrigeration is to cool liquid'ish foods in a thin stainless steel bowl on a cooling rack with a fan blowing on it, periodically stirring the contents of I'm in the kitchen, before popping it into the fridge. Cools quick enough that it's typically ready to go by the time I eat the meal & wash up the dishes.
Another consideration is that salt, sugar (in spite of being a nutrient), and spices in foods can act as preservatives. So David's jam on the counter sounds safe enough, especially given that he eats it up in fairly short order.