Not all hard-won knowledge ages the same way. Some of it lasts a whole career — how people behave, how to read a trade-off, how to break a hard problem apart. Some of it is stale within a year — the syntax, the tooling, the "right" way to do things in a world that no longer exists. A project built five years ago ran on different technology, different costs, and a different ecosystem than you'd reach for today. This tool is a way to tell the two apart — so experts don't get trapped by their own past, and newcomers know when to listen and when to forge a new path.
Like a radioactive isotope, a piece of what you know loses half its value over some span of time. That span — its half-life — is wildly different for different kinds of knowledge. Drag the slider to move through the years and watch the four tracks separate.
Lay the things you might "know" along a single axis: how long until half of it is out of date. On the left, knowledge with a shelf life measured in months. On the right, knowledge that barely moves in a career. Tap any point to see why it sits where it does.
Tap a dot to read it.
The fast-decaying things are almost always specifics — this tool, this version, this year's best practice. The durable things rest on something that doesn't change much: human nature, incentives, maths, the physics of systems. Tap any dot above.
Here's a stack of things people say with the confidence of experience. For each one, decide: is this durable wisdom that still holds, or a dated specific that the world has moved past? The skill you're building is the sort itself.
Get the half-life wrong in one direction and you cling to something that expired. Get it wrong in the other and you throw away something that still works. Each has a name, a set of tells, and a fix.
You treat a short-half-life fact as if it were a permanent truth. It was true — on the technology and economics of the time you learned it. The lesson outlived the conditions that made it true.
Tells
You treat a long-half-life truth as if it were a fad, because it came wrapped in old packaging. So you rediscover — painfully — something people solved decades ago, and call it new.
Tells
You've got a specific call in front of you and a piece of experience pointing one way. Should you defer to it, or trust that the ground has shifted? Answer for the decision you're actually weighing — the needle moves as you go.
Most real calls land in the middle: keep the durable principle, and forge your own path on the specifics the world has changed.
The hard part isn't the idea — it's applying it in the moment, on your own experience, when your confidence is loudest. Teams that do this well move fast without relearning old lessons, and respect their veterans without being anchored by them. That's the work we do with the leaders and teams we coach: turning hard-won experience into judgement that keeps compounding.
Talk to us about coachingWhen experience speaks, ask first: is this a durable principle or a dated specific? Defer to the principle; verify the specific against today.
How sure someone sounds tells you nothing about how fast their knowledge decays. Judge the claim by the thing it rests on, not the delivery.
Invest most in what lasts — judgement, systems thinking, how to learn. Those curves barely decay, so every year on them stacks.