A Risk Number Does Not Decay on a Smooth Curve
An annual quantification gets produced in March and quoted as fact in November. Everyone involved knows the figure has aged and nobody knows by how much, so it keeps being presented with the same confidence it had on the day it was signed off. The usual framing is that a number decays gradually and needs refreshing more often. The framing is half right and it misleads on the part that matters, because most of the decay does not happen gradually at all.