Congratulations Judy and Gizmo! I know EXACTLY what you mean.
We had our own celebration the other night. For all his life, Ozzie cannot go in our finished basement because he pees on the carpet. Nowhere else in the house anymore (not for years, except on his designated papers) but always down there. Every time.
My mom let him down the other night where he had come to visit me (trimming out our new closet) and not only did he NOT pee, he came up the stairs BY HIMSELF -- something he never does -- so I came and opened the door for him and he went right to his papers.
Much happy dancing and praising here. It only took 10 years!