In the 1960s, when the antis were talking about banning or taxing ammo, I made a point of keeping a year's supply in reserve.
In 1968, when ammo sales were restricted to FFLs and ammo sales were logged in a bpund book, I developed a habit of buying cartons of ten boxes rather than single boxes.
In the 1980s, when the antis were talking about banning or taxing ammo again, I made a point of keeping five year's supply (esp. .22LR, 12ga and .30-30) in reserve.
In the 2000s when I was involved in modern and vintage military matches at the local club, I discovered that supplies of .45 ACP and .30 Carbine could be spotty: apparently manufacturers based their manufacture on last year's sales, and apparently did not factor CMP sales of M1 Carbines into their production projections or the uptick in CMP matches. SO I learned to lay in a two years' supply for each gun I used when prices were low and availibility was high. And buying through Wideners and driving out to pickup. I also bought a CZ52 (2004) and a 91/30 (2008) since 7.62x25 and 7.62x54R ammo was always cheap and available, and even there I laid in enough for at least two seasons.
Long story short: Ammo shortage? What ammo shortage? (gloat, gloat)
(I can reload 7.63 Mauser, .38 Spl, .45 AutoRim, .30-30, 6.5mm Carcano, .303 Brit, .30 Carbine the classic Lee Loader way if necessary).