Yeast cells are some tough lil critters. If it's too hot,they die. If it's too cold,they go dormant. I've read stories on here where beer sat in primary for 5 months or more,& still came out good.
By & large,this question is def in the gray area. There lifespan is relavent to the conditions they're in. For most ales' time in primary,I don't woory about it.
Everything works if ya let it-Roady(meatloaf)
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