As a poet, you need mental stimulation. One way of doing that is occasionally working with someone new. Not every one of these experiences will be good, but they will all help you grow and learn. Even if you do have a long-term writing partner, it can be good to shake things up a little and work with someone else. Maybe you and your partner could collaborate with a third person. You might consider making a goal of working with a certain number of people in a year or collaborating on a certain number of poems. The goal will help you focus.