Most of the differences in building engines for off road SCORE or desert endurance racing purposes, say experts, concern the endurance factor. The annual Baja 1000 is actually 1,300 miles of punishing off-road racing. The winner will take 25 or 26 hours to complete the race, so the engines have to last for that long.
Double-dipping will make food go bad faster because it transfers saliva into the food, which promotes bacterial growth. One study even found that three to six double dips transferred about 10,000 bacteria from an eater's mouth to the dip sample. Putting leftovers away in a big clump may also promote food spoilage.
Best before is not the same as expired. Just because it says best before 5 Feb 2012 doesn't mean it's suddenly going to go bad on 6 Feb 2012. As long as I'm careful with the contents and avoiding contamination (for example, not sticking a used knife or spoon in there) it'll last long past the best before date. I've had jars 3 months past the best before and zero ill effects.