We stock up on things we constantly use, and rotate it. If it has a shelf life of 12 months, then we do not buy a 24 month supply. For most things, we get them on sale.
We have a well, and we do have some water filters, but they are not totally necessary, hence we don't have a lot. We have been exploring how to get water from the well in case of a long time shut down of electricity.
We also have a creek on our other property, instructions for converting such to safe drinkable water. We have rain barrels that could be used to haul water etc etc-I won't bother you with further details.
But anyway I do think it is important for everyone to sit down and think what if all modern technology was gone overnight or too expensive for you to buy. How would you survive independently? Focus on food, water, shelter, meds, protection, and hygiene(not necessarily in that order).
Keep your well, but don’t trust it. Even a little bit of arsenic leeched into the water can be very dangerous. It has been found that it inhibits the immune system so that it doesn’t recognize pathogens fast enough.
http://water.usgs.gov/nawqa/trace/arsenic/
There is an old trick used in Mexico that is impressively good in purifying water. They would hollow out a big block of limestone, then form the other side to a point. The water that seeps through is sterile, particulate free, de-metalized, pH neutralized, and about as good as it gets short of a Z-filter. Good for thousands and thousands of gallons.
As far as fuel goes, I am very fond of commercial column stills, which can produce a goodly amount of alcohol.
For very high temperatures, a Fresnel lens from a flat screen TV can give you a point temperature of about 2000F, enough to melt copper, lead, aluminum, and tin. While you’re wearing welding goggles.
For medical gear, there are fairly inexpensive oxygen concentrators for sale, which can be a lifesaver when someone has lung problems.
Twenty mile range walkie-talkies are less than a hundred dollars.