  A growing body of literature examines the effects of superdiffusive
subballistic movement pre-measurement (ageing or time lag) on observations
arising from single-particle tracking. A neglected aspect is the finite
lifetime of these L\'{e}vy walkers, be they proteins, cells or larger
structures. We examine the effects of ageing on the motility of mortal walkers,
and discuss the means by which permanent stopping of walkers may be categorised
as arising from `natural' death or experimental artefacts such as low
photostability or radiation damage. This is done by comparison of the walkers'
mean squared displacement (MSD) with the front velocity of propagation of a
group of walkers, which is found to be invariant under time lags. For any
running time distribution of a mortal random walker, the MSD is tempered by the
stopping rate $\theta$. This provides a physical interpretation for truncated
heavy-tailed diffusion processes and serves as a tool by which to better
classify the underlying running time distributions of random walkers. Tempering
of aged MSDs raises the issue of misinterpreting superdiffusive motion which
appears Brownian or subdiffusive over certain time scales.
