We study multi-year cycles (MYC) in sea ice with the Semtner-0-layer and the Bitz and Lipscomb 1-d thermodynamic sea-ice models. We investigate the length of the MYC, their stability to perturbations and the role of snow precipitation. We find a large wealth of different MYC the lengths of which depend very delicately on the external forcings. We discuss the possible consequences of these findings for observations of sea-ice variability in the Arctic.