I work in an area with really bad cell reception. So bad my phone also struggles. Surprisingly I can go for a run and stream Spotify and rarely get an interruption. I think it’s able to cache enough of the track fast enough to get me through the areas where the service gets really bad.

Another observation I made is I recently switched to T-Mobile which also has bad service where I work but much better than ATT. Suddenly my battery is doing dramatically better. Even on days I don’t run or stream at all. I figured that LTE sat idle if your watch was near your phone and/or connected to WiFi.