The survival curve
One cohort of — coins, launched between — and — ago, followed forward through its own history. For each, every swap it ever had — so a lifespan is simply the time from launch to last trade.
This follows one set of coins forward, so no threshold enters the definition and no cross-sectional caveat applies. The point at launch is the share that outlived its own creation block — a little lower than the share that ever traded, because — coins had every one of their trades inside that first block. Coins still trading when the chain was scanned (— of the cohort) are counted at the lifespan observed so far, which can only pull the median down, never up. Each point divides by the coins old enough to be eligible at that age, not by the whole cohort.
How firmly is the median known? On this scan the 95% interval runs —, from order statistics — both ends are real lifespans out of the cohort rather than a modelled curve. It will tighten as history accumulates and successive cohorts can be pooled.
Dying gets slower
Each step below strands a smaller share of the cohort than the last, and takes longer to get there. Over most of the range that means a coin which has already survived a while tends to have longer left than one that just launched — read the table underneath for the actual figures rather than as a law, because it is measured, not modelled, and does not rise at every single step.
How much longer?
Of the coins that reached a given age, the median time they went on to last. Straight from the cohort, no model fitted — and a statement about the cohort's dead coins from a past six hours, not a prediction about any particular one. Nothing here says what any coin will do next.