The red angus guys have been tracking actual longevity for a long time now. I think they can legitimately offer longevity.
My bro in law is that tall vet in the flint hills. We've discussed this longevity issue for 20 years. My/our solution is to leave Bulls out for 120 days. Pair out, and swap the late calvers as pairs for a pretty decent price. This plan doesn't holdup when cows and all beef are cheap, but then holding replacements are also cheap.