This sentence may come from a modern romance novel or an online novel, and its meaning may vary according to the context. The literal meaning of "work together for the rest of your life" could be interpreted as "spend the rest of your life together", implying that the two of them would spend the rest of their lives together and establish a deep relationship. This sentence might imply that the two people were already in love and wanted to spend the rest of their lives together to build an eternal love. However, the exact meaning of this sentence depended on the context. It could just be a romantic confession or a teasing tone, so it needed to be understood in context.