I just threw out some sour sour cream. It tasted rank! Opened, refrigerated but forgotten for weeks. no mold, though. Just sour and rank.
I would totally eat that shit, Diosa, and my apartment is usually about 75F. Of course, I’m one of those crazies who makes soups and stews in a large dutch oven and then leaves them on the stove to cool overnight before decanting to smaller containers and refrigerating. According to some folks, I should have died a long time ago!
My boyfriend is a stickler for expiration dates, but I just ignore the numbers and go with the sniff and taste test. Sniff first - if the smell makes you gag, throw it out. If it smells okay then stick a spoonful in your mouth. If it doesn’t make you gag, you’re good to go.
I like to live dangerously.
If they were still cold, I’d think they’d be fine.
I’m with Hazel on relying more on my nose/eyes/tongue than on expiration dates. Never had food poisoning that I know of. 
Haven’t we long since decided that commercial mayo inhibitis bacterial growth? For example, here’s an article from 1982. Or here from 2008.
Traditionally, isn’t yogurt supposed to be able to survive being stored in animal stomachs hanging from your saddle, while crossing the desert? I think it ought to be able to survive an evening on the kitchen counter, especially in the OP’s Arctic house. 
Many pathogenic bacteria produce substances with a foul odor and taste, but that isn’t universally true. However, expiration dates are based on worst case bacterial growth and/or detrimental rancidification (oxidation of lipids). It is actually the latter that is likely to cause the foul odor in fatty dairy products, and while it may be unpalatable if you are unaccustomed it doesn’t compromise a health hazard (though it does indicate that many of the vitamins are probably degraded). In short, smelling a questionable piece of food is no guarantee that it is not colonized by bacteria.
Yes, commercial mayonnaise has inhibitors and preservatives which limit both bacterial growth and rancidification. Think about that for a minute; there are chemicals added to the mayonnaise designed specifically to prevent utilization and keep fats from breaking down. Do you think that also prevents the substance in question from being digested, and may also inhibit effective digestion and utilization of other nutrient substances consumed along with it?
Yes. Of course, the yoghurt product you are writing of resembles a plastic cup of Dannon yogurt like a Scottish bogland resembles a well-manicured golf course . Traditional yoghurt products are very sour, have virtually no lactose or other sugars, smell like musty cheese, and are of the consistency of soft tofu. Most people used to modern foods would find it inedible (although some would find it like a more flavorful and textured version of acidified buttermilk).
Stranger
No. Because actually, that’s not how the preservatives work. I checked the ingredient list of Hellmann’s mayo, and the only preservative it has (besides vinegar, which of course nobody’s going to have a problem with) is calcium disodium EDTA. It binds to trace metals in the mayo and keeps them from oxidising. No, it’s not stuff that’s gonna taste great and like anything else is toxic in high doses, but it’s used in medicine for chelation therapy (heavy metal poisoning treatment) for the exact metal-binding properties that it has in food. It doesn’t keep fats or anything else from being broken down by your digestive acids and enzymes.
I’ve also never crapped out a wad of mayo-filled chicken salad that appears untouched, either, so it appears that everything’s getting digested pretty well.