Last couple years forced me to rethink a few things. I live in the suburbs of a moderate sized city, but have several hundred acres of farmland a couple hundred miles south with a place to stay, well water, septic system, small wind turbine, solar cells, and 100 acres of woods with a wood burning furnace + stove. Have the wind turbine and solar cells because I'm only down there about 1 month a year to look over the farming operations (we rent it out). So we sell most the electricity we generate back to the coop. Then at harvest time, we usually break even when it comes to running the motors for irrigation and driers in the bins.
I have the guns from my grandfather, a double barrel 12ga goose gun, a .22 Stevens single shot rifle, 1903 Springfield, a M1911, and a Walther PP trophy gun from WWII plus I have a AR, 2 9mm pistols for CCW (same model), a Mosin Nagant, a .38 revolver, and a .40S&W pistol. I figured the common thought of "Keep standard calibers and you'll be able to find ammo" was a good one. I used to keep enough ammo around to load magazines once. Basically enough that if I wanted to run to the range and didn't have time to stop off at the store to pick up ammo I could. The most I kept around was about a brick of .22 that would last me a year.
Well when the craziness happened after Sandy Hook the only thing I could find regularly was .40S&W and 30-06 Springfield. I sold one of my AR's during that time for nearly 3x what I paid for it. I kept the money in a savings account and recently bought a second safe for ammo. In the past few months I've probably bought enough ammo to be on a watch list as I've stocked up on 3000 rounds of 5.56, 3000 rounds of 9mm, 1000 rounds of .40, 250 rounds of .45ACP, 880 rounds of 7.62x54r, 300 rounds of .38, and 200 rounds of 30-06. And I intend on keeping this supply as reserve and not to shoot. If .22LR ever comes back into stock (hoarders are the main problem right now), I'll probably stock up of 5,000 - 10,000 rounds of that over time. (buy a brick a week for a couple months).
Five years ago I wouldn't have done that.