I find that using an Apple Watch with my phone was draining the battery really fast, I can’t say if Shokz bluetooth connection would do the same.
If it is really cold, try to keep your phone warm.
Try not to use your phone too much while waiting in the corrals.
If the brightness of the display can be turned down while still being visible, great.
I ran 6 marathons with NRC and Strava running, plus I took pictures, and never had a problem with battery.
There’s a few things that come to mind that you could do to increase battery life
- Use low power mode. This will keep background apps from refreshing but I don’t think it will impact your active apps. You may want to give it a test run

- Download the music to your phone so it’s not trying to use the cell connection. This will help even if you choose not to follow #3.
- Turn off the cellular data connection. You can still use gps so I assume NRC will still work but another thing to give a test run.
That reminds me, make sure that the auto-pause is off for a race.
Low Power mode and reduced cell downloads can help, test them first to be sure NRC still measures the way you are used to. I vaguely remember something becoming finicky in the Low Power mode.
You might loose a lot of accuracy if you turn cellular connection off.