To improve sustainability of egg production, current practices in the table egg industry aim at lengthening the egg laying cycle of commercial hens from 70-80 to about 100 weeks of age. In such a context, the control of eggshell quality is the limiting factor of extension of the laying cycle rather than the egg production persistency itself. The aim of our study was to precise which traits of eggshell quality were the most affected by hen ageing, in order to identify which physiological mechanisms were affected and need to be amended. We have investigated the effect of layer age on various eggshell quality parameters (shell breaking strength, dry weight, thickness and toughness) by comparing eggshell of commercial hens reared in cage-free system at 32-34 (peak of lay), 71-73 (late laying cycle) and 94-99 (very late laying cycle) weeks of age. As expected, eggshell breaking strength and thickness significantly decreased during the laying cycle: -17% and -27% for the breaking strength, and -4% and -12% for the thickness, respectively at 71-73 and 94-99 weeks of age. Interestingly, eggshell weight was significantly lower at the oldest age (about -7% at 94-99 weeks). Eggshell toughness was decreased by 12% 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 shell and to the shell fabric, which comprises the morphology, size and orientation of crystals that define the shell texture and ultrastructure. As the hen ages, shell mass remains constant until 71-73 weeks of age, while egg weight increases, resulting in a reduction in shell thickness. The decrease in 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 shown by the decrease in shell toughness. However, the further reduction in shell biomechanical properties in older hens (94-99 weeks of age) seems rather to be attributable to a decrease in shell mass combined with changes in the ultrastructure of the calcite crystals making up the shell. As shell mass is critically affected at the end of long laying cycle, particular attention must be paid to monitoring calcium metabolism and transport in long-life layers. Further studies are needed to explore the underlying mechanisms leading to eggshell degradation at 94-99 weeks.