The laying hen uses large amounts of calcium each day to form the eggshell which is composed of 95% of calcium carbonate on calcitic forms and 3.5% organic matter that directly influence the biomineralization process. Shell mineralisation occurs at night when the animal has no access to feed. The calcium is then taken from the bone which is regenerated during the day. For reasons of sustainability, commercial laying hens are being reared later and later, but as they become older, calcium metabolism deteriorates, leading to shell strength defects and spontaneous bone fractures. In this work, we investigated the effect of such extension of the laying period on the eggshell quality. Commercial laying hens were reared in cage-free system to 32-34 (peak of lay), 71-73 (current laying cycle) and 94-99 (extended laying cycle) weeks of age. Eggshell quality parameters (breaking strength, dry weight, thickness and toughness) were determined on eggs collected at each period of age. As expected, eggshell breaking strength and thickness significantly decreased during the three tested periods of the laying cycle. More surprisingly, eggshell weight is significantly lower at the oldest age (94-99 weeks). Eggshell toughness is decreased in both 71-73 and 94-99-week-old hens, when compared to 32-34-week-old hens. Eggshell mechanical properties are due to the mass of materials and to the fabric of the shell. The latter comprises the morphology, size and orientation of crystals that define the shell texture and ultrastructure. As the hen ages, shell mass remains constant, while egg weight increases, resulting in a reduction in shell thickness. The decrease of eggshell mechanical quality parameters observed between 32-34 and 71-73 weeks is likely due to this decrease of shell thickness combined with modifications of the shell fabric and eggshell texture as observed by the decrease in shell toughness. In older hens (94-99 weeks of age), shell mass is reduced. This effect on shell mass was not reported earlier likely due to the absence of measurements at this advanced age. This decrease in mass, combined with changes in the ultrastructure of the calcite crystals making up the shell, leads to a further reduction in the shell biomechanical properties. Structural and molecular studies must be performed to further understand the mechanisms leading to eggshell degradation at 94-99 weeks and to identify potential levers to lower negative impacts on eggshell and bone quality in extended laying periods.