  I report new, world-leading LHCb results on heavy meson lifetimes. We use a
novel approach that suppresses the shortcomings typically associated with
reconstruction of semileptonic decays, allowing for precise measurements of
lifetimes and other properties in collider experiments. We achieve a 15% and a
$2\times$ improvement over current best determinations of the flavor-specific
$B^0_s$ lifetime and $D^-_s$ lifetime, respectively.
