Sticker, you said it all with this
" How in the world can an animal last an hour without being able to breathe?"
It can not.
All muscle needs oxygen to function. If the lungs are collapsed after a true double lung shot there will be no oxygen to the muscle/brian, and those muscles include the heart. The animal will die. If the animal doesn't die it means the shot did not completely collaspe both lungs. It may have touched both but did not puncher/collapse them or cause then to stop functioning completely.
An animal with a heart shot from a broadhead can go for miles since the heart in most animals only has to function at less than 50% in nornmal activity. If it is still functioning near that it can still travel. Once it bleeds out there is nothing to carry the oxygen to the muscle and brian and the animal dies.
Sometimes what appears to be a double lung shot isn't that at all.
Work hard and be true to yourself.
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