[en] The existence of both size and “even-odd” effects for the lifetime of carbyne-based nanodevices consisting of two graphene sheets connected by a carbyne chain is predicted. Based on the results of DFT-calculations, it is ascertained that appearance of a region where equilibrium positions of atoms are impossible is a key feature of the failure of carbyne-based nanodevices under mechanical loading. This region appears before the chain is broken. It is the reason for the effect of mechanical load on the “even-odd” effect for lifetime. For a wide range of temperatures and mechanical loads, a lower estimate of the lifetimes of carbyne-based nanodevices is given, which supports the possibility of their practical use.