Somewhere I've read of a serious shooter who deliberately loaded his cartridges long if they weren't to be used right away. He'd seat to the correct depth before going to a match.
I've read the same. Don't know if it's the same source, but it's a good idea.
In all my years of loading/shooting/hunting it has only happened to me 1 X.
They were 06 loads that had been loaded more than 2 yrs.
It is real as is evident from the responses here.
Jerry