I shoot far more than 20 to sight in. I fiddle with the range, scope variables, and somethims shoot just for the fun of seeing what I can do.
When the shtf, one old man with a single shot rifle will probably last until the gun is empty. That does not mean that others should not have the means to do whatever they think is necessary if the time comes.
I still enjoy reloading so will have to watch the primers, powder, and bullets. These things have just recently come into decent supply, if not pricing.