We stock and store extras for a rainy day. We have plenty of food and seeds to grow more. We have guns and ammunition. We have batteries and toilet paper. But things don't last forever. Things fall apart.
Improperly stored ammunition will bulge, corrode, mold and could lose its potency.
Rechargeable batteries can be recharged only so long before they stop holding their charge. This includes car batteries and deep cycle batteries.
Springs fail. The springs in your magazines are most at risk. Even keeping spares unloaded is no guarantee the springs will last for ever.
Toilet paper, tissue, firewood, lamp wicks and petroleum products can only be used once. They can never be recycled and used again.
Bagged fertilizer only lasts so long in sitting in the garage.
Medications have a shelf life. Afterward, some go bad quickly, but most lose their effectiveness slowly over time. First by half, then another third and downward from there.
Some canned foods last five or more years, but most will be inedible in three years.
Only sugar and salt and a few other dry, processed foods last a long time. Most go rancid in a year or two.
Light bulbs break or burn out, fuses burn out, wiring corrodes, switches break. Most basic electrical equipment will cease functioning in a few years without replacement parts.
House foundations crack, sag and fail. Roof shingles need replacing every ten years or so. Once a window breaks, a new one cannot be made from the old. The average home has to have constant maintenance or it will rapidly fall apart.
Once the SHTF, things will start to age and if infrastructure is down or destroyed, then replacements are not coming. The clock will start to tick on everything and if ignored, will never function again.
That goes for people too. When that trained mechanic, or doctor or farmer dies, then all that knowledge goes with them and there will be no schools producing another to take their place.
For the long emergency, be prepared to do without sooner or later. Figure out what to do when gasoline is gone and batteries lose their charge. What will you power the home with? How will get from one place to another? What will you put on your feet?
It's mind boggling and troubling at the same time.