  We assess the current coverage and the future discovery potential of LHC
searches for heavy Higgs bosons decaying into long-lived particles (LLPs),
focusing primarily on the production of pairs of LLPs with hadronic final
states. These signatures are generic in dark sectors where a heavy scalar
decays into pairs of lighter states which subsequently mix with the Standard
Model Higgs. We show that a handful of existing analyses provide broad coverage
of LLP decay lengths ranging from millimeters to tens of meters, and explore
the complementarity between searches for displaced and prompt final states in
several simplified models. For both heavy singlet and heavy doublet scalars,
LLP searches typically provide the leading sensitivity in current data and
exhibit the strongest discovery potential in future LHC runs. We further
translate the impact of these searches into the parameter space of various Twin
Higgs models, demonstrating that LLP searches are a promising avenue for
discovering a Twin Higgs with displaced decays. Finally, we propose a variety
of additional search channels that would improve coverage of the second Higgs
at the lifetime frontier.
