Ah yeah, along that geodesic, which is far from the total of the universe. But I think I now understand that meant "total duration of the existence of the unive

Ah yeah, along that geodesic, which is far from the total of the universe. But I think I now understand that meant "total duration of the existence of the universe". I think an answer to that question depends of what you mean by total duration of the universe. If the photon never gets absorbed by anything, then it goes in forever. If it exists then the universe still exists forever since at least one photon exists forever.