Oddly I have a coworker who bought a caramel apple and then left it in its plastic on his desk for about 4 years. We didn't photo document its decline but I should be able to recall.
After about a week the impalement point became quite unappealing. The area around the stick darkened and softened (it seemed, I didn't touch it). The rest of the skin looked fine.
After several years the caramel looked perfectly fine but misshapen and the apple had dried and shriveled inside of it.
Based on that, and my own experience, I would conclude that a refrigerated caramel apple would have about the same life as an uncarameled apple except for the core which would need to be avoided.
As for extending the life? Perhaps pour wax around the stick entry point to buy yourself a couple days?
There is a possible case that the butter isn't old. McGee writes that butter made from unpasteurized cream should be eaten within 10 days, else its unique aroma is lost. Maybe the addition of salt and/or other preservatives stretch that to over 20 days, or the manufacturer is being optimistic.
On the other hand, even if the butter is old, there is no need for concern. Butter doesn't catch germs or molds. It can go rancid, but this is a chemical change, which happens slowly. The affected parts are visible, and after removing them, there is no problem with the remaining butter - this is no invisible penetration as with mold. The butter must get really old (maybe > 6 months) to get small pockets of rancidity on the inside which are too much trouble to remove. And even if they aren't removed properly, eating small amounts of rancid butter isn't a health concern (although the taste is ruined).
Butter also doesn't undergo signinficant changes when it ages - it isn't like eggs, which are good to eat for weeks, but behave differently when fresh. So eating old butter isn't worse than eating fresh butter (with the exception of the raw-cream butter mentioned above).
For these reasons, I wouldn't worry about the butter. Unless it was sold as raw cream butter, it is probably old stock. But it is still good to eat, and will be good to eat well past its stamped date. If it should develop an oxidized layer on the outside, just cutting it away will be good enough.
Best Answer
I agree with Jay. If you live in a hot city (with temperatures above 30°C), I wouldn´t keep it out of the fridge more than a couple hours. Otherwise they should last at least five hours at room temperature.