Advancements in technology enable integration of a large number of cores on a single silicon die. At the same time, aggressive technology scaling has an ever-increasing adverse impact on the lifetime reliability of such large integrated circuits. In this work, we model the lifetime reliability of homogeneous manycore systems using a load-sharing nonrepairable k-out-of-n:G system with general failure distributions for embedded cores. In manycore systems, an embedded core can be in operational, cold standby, or warm standby state depending on system redundancy schemes and their workloads. We then use the proposed model to analyze the impact of different redundant schemes and configurations on the lifetime reliability of manycore systems.