Personally I treat my relationships with the gods as I do any other relationship I am a part of in my life. It's been this way for me since I was a girl. When I work with the energies of deities they are personified. Each god is given a visual image in my mind as I work with them. I have always interacted with the gods in this manner as it enables me to treat the relationship as if it were manifested in the physical realm. The Christian god appeared to me as a kindly Grandfather image and Jesus appeared to me as an older brother and in later years a peer.
When it came to the time where I felt a relationship was dwindling or that my time spent with a particular deity was complete I would respond in the same way I would when I found I was spending less and less time with a friend. Unlike friends I've had in the past, I would never feel angry or upset ... I recognized that during my life experience there would be times when a friend and I would part ways because our lives were taking us in different directions and when this would occur I would be saddened that we were parting ways, but happy that they were living life in accordance with their desires. This was the same way I felt when my time with a god or goddess was ending. I would take time to honor and celebrate what we shared, as well as honor the parting. I don't feel that the gods I've worked with are ever truly gone from my life ... more like they've stepped back and are in the peripheral of my spiritual life; observing and holding "space" for me so that I may experience life with my new gods and grow as a complete human being. It feels as if I am building my own pantheon of gods that are bound together through me even if they are of different cultures and spiritual traditions.
Practically when my relationship ends or shifts with a particular god or goddess I hold a ritual and thank them for the time they spent with me, for the energy they expended on our relationship, and the wisdom they've bestowed upon me. I give them an offering and release them as I would if I had evoked them within a cast circle, but as I've already expressed I feel as if they are always with me.