I don't keep much loaded centerfire ammo on-hand. But, I do keep a reasonable amount of reloading components.
At my normal rate of consumption, I have enough rifle and handgun components to last about 2-3 years. Shotgun components would last about 7-8 years.
.22 LR and .22 WMR are the only things I keep a fair amount of on-hand.
I'm somewhere around 1k rounds of .22 WMR and 9k rounds of .22 LR/.22 Short.
I can't afford to do a 2-for-1 replacement, when I shoot; but I do try to replace components or rimfire ammo with more than what I used. I may now be at a point where I can stop doing that, and just go to a one-for-one replacement.
"Such is the strange way that man works -- first he virtually destroys a species and then does everything in his power to restore it."