And with my Garmin I figure I’ll get around 15 hours (even if it says low battery at 10), so if I expect the ride to be longer than that I’ll start the ride with the Garmin running on a USB battery, and then once I get to ~15 hours remaining, I’ll stow the battery/cable. Easier to put the battery away than dig it out.
If there is a sleep stop, or some extended time off the bike, I’ll dig the charger out and charge the Garmin/phone then, and stow the battery/cable when I resume.
If the ride is long enough that that battery isn’t enough, then the USB battery gets charged with a USB-Werk on day two.