In order to design marine renewable energy mooring systems which are both economical and durable it is necessary to establish the lifecycle performance of individual components. In parallel with numerical tool development, physical component testing utilising realistic load cases is pivotal in achieving a greater understanding of performance variations including the contribution of degradation mechanisms. Building upon previous experimental tests conducted by the authors, tension–tension tests were conducted on a sample used in first part of the study and samples extracted from a mooring line which was deployed for 18 months with the South West Mooring Test Facility. In agreement with the first part of the study it was found that sample axial stiffness and damping are influenced by load history and instantaneous strain. The increased compliance, lower load bearing capacity and reduced tension–tension fatigue performance of aged specimens are symptomatic of fibre-on-fibre abrasion damage sustained in service. Visual inspections of the rope and yarns including scanning electron microscope analysis of fibres revealed that abrasion wear was accelerated by debris found within the rope structure, highlighting the importance of preventing particle ingress. Datasets are provided to facilitate the development of rope and mooring system simulation tools.