Flax fibre reinforced composites are demonstrating promising outcomes which makes them potential candidates to replace synthetic composites in various industrial applications. However there is limited information regarding their long-term performance. It is widely acknowledged that natural fibres are less resistant than their synthetic counterparts, so it is crucial to study their durability before considering their use for real applications in rehabilitation and strengthening of structures. For the above reasons, this study, lying within the framework of the National Research Agency project MICRO, aims to study and predict the performance of flax fibre reinforced composites with a bio-based epoxy matrix. This is achieved by exposing the bio-composite and samples made of bio-composite bonded on concrete slabs to different accelerated ageing conditions over a total period of 2 years, and with various combinations of temperature and relative humidity in the ranges 20°C-60°C and 50%-100% RH, respectively. Then a series of tensile, short beam and pull-out tests are performed periodically on the ageing samples. Finally, the collected experimental data are analyzed using a reliability method in order to evaluate the service lifetime performance of this new bio-based composite.