A method and corresponding device are disclosed for varying setup mode based on reported latency at a target device. The target device or its serving network may report a latency characteristic associated with the target device, such as an indication of the air interface protocol and/or slot cycle being used by the target device, and an initiating device or communication server may use the reported latency as a basis to decide whether to operate in (i) a normal setup mode when setting up a communication session with the target device or (ii) an optimistic setup mode when setting up a communication session with the target device.