Conventional searches at the LHC operate under the assumption that Beyond the Standard Model particles undergo immediate decay upon production. However, this assumption lacks inherent a priori justification. In this study, we focus on displaced decay signatures, investigating their potential in both current and future collider experiments. Specifically, we examine the interactions between inert Higgs doublet (IDM) dark matter and a vector-like $SU(2)$ triplet lepton (VLL), both of which are $Z_2$-odd. While the vector current of the $Z$-boson with the VLL rules out a fermionic or two-component dark matter scenario, a compressed mass spectrum combined with a small Yukawa coupling permits co-annihilation and late decay of the VLL into the IDM sector, impacting the relic density of the pseudoscalar dark matter. These conditions also allow for displaced decays of the VLL, resulting in distinctive hadronically quiet, displaced multi-lepton signatures. Such signatures are analyzed in the context of the 14 and 27 TeV LHC, as well as the 100 TeV FCC-hh.