  Among the several strategies for indirect searches of dark matter, one very
promising one is to look for the gamma-rays from decaying dark matter. Here we
use the most up-to-date upper bounds on the gamma-ray flux from $10^5$ to
$10^{11}$ GeV, obtained from CASA-MIA, KASCADE, KASCADE-Grande, Pierre Auger
Observatory, and Telescope Array. We obtain global limits on dark matter
lifetime in the range of masses $m_\mathrm{DM}=[10^7-10^{15}]~\mathrm{GeV}$. We
provide the bounds for a set of decay channels chosen as representatives. The
constraints derived here are new and cover a region of the parameter space not
yet explored. We compare our results with the projected constraints from future
neutrino telescopes, in order to quantify the improvement that will be obtained
by the complementary high-energy neutrino searches.
