After 20 years I quit. I was allergic to everything, had a cold every other month. After 2 years out I am allergic to nothing , I hardly catch a cold or get sick. I think my immune system was breaking down. My instincts tell me if I did it much longer I'd get cancer . Took a 4 year break then restored my 2 darts. It took awhile to get the knack of some things back .