If viruses died at a fixed timespan, I think that would point to there being a stateful element that keeps track of elapsed time, like a molecular sand timer.

If viruses died at a fixed timespan, I think that would point to there being a stateful element that keeps track of elapsed time, like a molecular sand timer. If viruses die because of spontaneous reactions, eg interaction with surfaces, interactions with photons, or a spontaneous chemical reaction like oxidation, then I would expect half-life decay similar to radioactive elements. I don't know how viruses die. I wonder if they can be preserved near indefinitely in a non reactive gas or vacuum in the dark.