A model of the evolution of the onshore wind turbine blade mass installed in Denmark is proposed described by a Weibull distribution and the age of the blades is estimated from decommissioning data to t_{50 %,onshore} = 29 years when half of the blade mass of an installation year has been decommissioned. This is considerable longer than the 20 year design life time of onshore turbines, which is often assumed to be an estimate of the End-of-Life of turbine blades. Thus blade waste predictions using the simple assumption may predict that installed blade masses are entering recycling processes about 9 years sooner that what is observed in Denmark. The blade mass for decommissioning in Denmark is estimate to peak at 2000 ton/year and 5000 ton/year in 2028 and 2045 using the Weibull model.