Dear Robert,
Well, Theosis is a life-long process - there is no real time when Theosis is achieved FINALLY in the life of a saint, unless, of course, we are talking about a saint who was a sinner, before his conversion.
Icons of Saints will often portray aspects of his or her life in the frame and the Saint will have a halo.
In St Nicholas's icons, sometimes he will be portrayed with a halo at his birth.
Both his parents are saints and there is a tradition that Nicholas was sanctified at his conception in the womb of his mother by the Holy Spirit.
It is there in the liturgical services, but it was never the subject of a doctrine etc.
Alex