The Skeeter's T/R blades have 1000hr. life and the pre mod. ones have 600hrs. till they are ready for the bin. In reality I would imagine the manufacturer allowed a large safety margin in this figure particularly as they were selling to the MOD and the MOD probably put in another safety magine as they were not paying for them. Amazing to think that they are made from laminated birch, Spruce and balsa wood and covered in fibreglass.