The normal life span is 1 to 3 months when used in areas more than 300 m2 in size and longer for smaller areas. The lifetime of the blades varies immensely and depends for instance on:
-Operating time and size of the working area
-Type of grass
-Type of soil
The presence of objects such as pine cones, toys, tools, stones, roots and alike on the lawn are likely to damage your mowers cutting blades and should be removed from the lawn regularly to avoid damage to your machine. You can easily replace the blades by yourself.