How Long Can Elidel Be Applied For Dermatitis Under Nose And Mouth?

I am using Elidel twice daily for a dermatitis under my nose around one side of my mouth. I have had this for at least 2 months and have been using Elidel for over a month. It fades at times and comes back with a vengeance other times. (I cannot find any patterns.) I live in Wisconsin and it has been a cold winter. I vacationed in Florida and Georgia for 4-5 days each time. The dermatitis immediately improved to the point I almost stopped the Elidel. As soon as I came back to WI, the dermatitis resumed. (No an option is not to move to Florida or Georgia.... :) How long can I safely use the Elidel? Thank you.