My mucocitis lasted for about 4-5 months after the last radiation treatment, but even after the sores themselves left, I had burning sensations on my tongue and other areas of my mouth off and on for some time. Even today, 5 years after treatment, that occasionally still happens. I always look to see if it is something there, but there is never anything visible. With xerostomia I am told, the papilla on the tongue get irritated very easily and it will be a life long occurrence, but these are irritations, not actually sores like mucocitis.