I strongly prefer shooting without having to turn the camera on and off all of the time since it interrupts shooting. It makes me start thinking about the camera as a pain in the ass rather than an extension of my eye. However, the Sony a7Rii forces me to switch it on and off between shots due to its terrible battery life. On the flip side, the Sony allows for the camera to be used and powered via its USB port. Knowing that shooting the Black Lives Matter protest was going to be a long and lively event, with no time to be worrying about turning the camera on and off, I grabbed a portable USB power bank to see if that could be any help.
I ran the power bank from my jacket pocket to my camera with a cord long enough to facilitate a full range of movement (overhead, down low, etc), and shot the entire day without turning the camera off but twice for about 5 minutes total. By the end of the day, I was absolutely floored by the results: all of my camera batteries were still fully charged and the power bank still showed 4 of 4 bars, indicating over 75% charge. I even charged my phone in that time. For the price of a single camera battery that might last an hour of continuous shooting, I came up with a solution that certainly seems like it could go a week straight. It makes sense though, the power bank I used was rated at 20,100 mAH and the Sony's batteries show 1,020 mAH.
The cord didn't get in my way and never detached from the camera (though if it did, the camera would have been fine on its own battery power). For the better part of the day, I forgot it was there. With all of pluses of the a7Rii, like perfectly clean ISO 12,800 that I used when it got dark, the biggest detractor has always been battery life—but I'm happy to have solved that issue for most scenarios. I can definitely see myself using this frequently, and running the battery cord from my backpack on days where I don't need a jacket. For tripod setups and shoulder mounts, running from an external battery is a no-brainer.