did it enable you to understand the relation between the poet and the speaker addressed in the poem?
did it alert you to the fact that the person addressed is young, happy and full of life and not yet old and gray and full of sleep?
I think you really need to look at the context of the poem. I think the idea of love being a concept as old as the hills is an apt one. Like so many of the poems in this collection, "When You Are Old" was written for Maud Gonne. It is based on Ronsard's "Quand Vous Serez Bien Vieille," Sonnets Pour Helene (1578), which maintains the Maud Gonne/Helen of Troy parallel that Yeats so often draws. The idea of love in age is an ancient one, meant to express the fact that love inheres not merely in youth, but in something deeper and more lasting.
Yeats capitalizes "Love," thus personifying the concept, which is is a nod to the poem's 16th century roots. Although monotheism had taken over Europe, Greek and Roman gods were very much a part of 16th century consciousness. Yeats's "Love" is a modernization of the ancient figure, Eros.
http://www.gradesaver.com/poems-of-wb-yeats-the-rose/study-guide/section12/
