Described are examples for techniques to increase service reliability by reusing session-stateful service instances within a single long-lived session. A system for routing sessions within a network includes a first server hosting a first instance of a first service configured to establish a first network session for a subscriber with a first instance of a second service. The system includes a second server hosting the first instance of the second service configured to select the first instance of the first service to establish a second network session for the subscriber. The second service may copy header information from a first session invite to a second session invite for the second network session. The first network session remains active for a duration of the second network session. Reusing the first instance of the first service reduces the number of potential failure points to increase reliability of the long-lived session.