[grobdriver]

.22 ammo stored for a couple years can have a high fizzle factor.

That has not been my experience.
I have several thousand rounds of CCI Blazer .22 - the cheapest stuff I could get - that's many, many years old, and every time I take out a box to shoot I've have zero failures.

[DuncanWaring]

I’ve got most of a 500-round box I bought about 15 years ago, (Remington?), brass-plated bullets, and lubricated.

It still shoots 100%.

The problem is that the lubricant has dried-out somewhat, and in a pump-action rifle I’ve got, after 10 or 15 rounds the empty case won’t extract; I have to push it out with a cleaning rod and clean the barrel.

[Cold Heart]

CCI has been reliable, other brands not so much. Not just my experience but many others. A lot depends on storage conditions. I have had match grade 7.62 go bad but that was 30 year old stuff. All had excess fouling and two misfire. out of twenty.