
No — dead is dead, and no treatment reverses it. But it does not automatically have to come down. A dead tree standing in open ground away from any target is legitimate wildlife habitat and can be left as a snag, or shortened to a safe height and left standing on purpose. The decision is set entirely by what sits underneath it, not by the tree's condition.
Months to a few years for most species with nothing beneath them. Dead ash is the sharp exception and compresses that timeline hard: EAB-killed ash goes brittle quickly, sheds limbs early, and becomes genuinely unsafe to climb, which is why crews quote it as a bucket or crane job and will decline to climb it at any price. Conks or shelf mushrooms at the base mean internal decay is already extensive and move the schedule up — but that is a 'book it this month' finding, not a reason to pay a 2am emergency rate.