The durability of Fiber Reinforced Polymer (FRP)-to-concrete bonded joints is crucial for the long-term performance of structural applications. This study investigates the effects of both accelerated and natural ageing on the integrity of this type of joints. In this study, double-lap shear specimens were subjected to accelerated ageing conditions, including various environmental factors, such as temperature fluctuations and moisture exposure, and for different number of cycles (100, 200 and 500 cycles). Laboratory tests aimed to replicate decades of exposure within a shortened timeframe, while field measurements monitored real conditions over time. Some double-lap shear specimens were instrumented with strain gauges in order to get the local deformation and local stress state in the bonded joint. Results focus on average shear stress, failure load, failure mode, and changes in glass transition temperature after ageing. For natural ageing, five bridges in varying environmental conditions were monitored to evaluate failure modes and adhesion capacity. The results obtained from accelerated ageing tests make it possible to define a number of cycles above which the durability of bonded composite reinforcement is attested. Observations from natural ageing are reassuring, as they do not reveal any significant degradation in the adhesion capacity of CFRP reinforcements. This research highlights the importance of considering both accelerated and natural ageing in the design and application of FRP-to-concrete systems. These findings gained contribute to best practices for the use of FRP in construction, ensuring enhanced structural longevity and safety.