I've had the same concern with my .41 MAG loads for years now.
Here's how I finally solved it :
I'd been flattening the primers in my M415 for months no matter how low I went within reason, they still went flat.
But in 8-10 reloads, the cases never split and neither did the primers.
So I figure, in that gun, primers flattened means next to nothing.
An old west lawman once said when asked why he carried a .45, "because they don't make a .46"