I've killed in the neighborhood of 30 black bears, some on bait, but mostly spot and stalk. For me, 80% of the time it's a one shot deal, but bears have seldom dropped on the spot and usually run a ways, sometimes quite a ways, even with a perfect double-lung shot.
Here and there, one really hangs on and takes a surprising amount to stop. Overall, they hang on a little longer and are tougher to stop than a similar sized deer and I've learned that if you have the opportunity for an "insurance shot", take it.
