In Lacanian theory, the mirror stage first becomes effective when the infant ego is confronted with the possibility of another ego - an other - usually taken as the gaze of the mother; but this is but a moment in the life of the ego; Can this stage of mimicry & mirroring be traversed (in more minor modes) as an adult? That is the mirror stage happens not once, but again & again; with the first (traversal) being the most important, later ones less so (thus minor); to put it another way - does remain active as a permanent part/conditioning of the egos structure & formation - at times more active at other times less so - rather than a transient formation in the egos early life; if so, under what conditions does it heighten or intensify?
Wikipedia suggests that it is:
Initially, Lacan proposed that the mirror stage was part of an infant's development from 6 to 18 months, as outlined at the Fourteenth International Psychoanalytical Congress at Marienbad in 1936. By the early 1950s, Lacan's concept of the mirror stage had evolved: he no longer considered the mirror stage as a moment in the life of the infant, but as representing a permanent structure of subjectivity, or as the paradigm of "Imaginary order".