Durability
Build what is intended to endure: never be a forced seller, and prefer the layer everyone must use to the product everyone can see.
Durability is chosen at the layer, not at the product. The preference is for the thing everyone in a category has to use over the thing everyone can see — identity, settlement, a register, a standard — because that layer survives the technology that made it necessary and usually the founders too.
Never being a forced seller is the structural half, and it is what turns a downturn from a threat into a purchase. It is also the claim most easily made and least often true, which is why the register that would expose it — every position, including the impaired and the written-off, with the recovery ratio never published alone — is published rather than described.
The format layer is built the same way. The record emitters import nothing but language builtins, so a company adopting one needs no toolchain and inherits no dependency this office could later break; the sealed entries do not decay; and the proof an early participant holds stays good after the estate grows, because growth adds a tier rather than revoking one.
What it refuses
A position that can be forced. Nothing obliges this office to sell, and any structure that would introduce that obligation — a fund life, a redemption right, a covenant with a date — is declined rather than priced.
Where it is practised
Nothing obliges this office to sell, which converts a downturn from a threat into a purchase — the single structural advantage the rest depends on.