It will depend on the use and care of the glasses. If you use alcohol to clean the lenses, the treatment deteriorates sooner, if you also rub the lenses very regularly that layer will come off much faster or if you neglect the glasses and the treatment is not very good this can also affect the duration. At Pegaso we give a 2-year guarantee on our protection lenses and 1 year on the anti-fogging treatment applied to them.