Ian's post was spot on. The run time with a quality 18650 like an AW IMR would be hard to top. If that doesn't get ya thru, can't think of much else that would
Not to mention the durability - can't think of anything that even comes close to that offered by a metal REO. I mention that because you are in and out of different rigs throughout the day and it sounds like your chances of your mod hitting the ground are increased.
That's the beauty of having a small form factor, and juice in the mod rather that on it - if it drops, most likely you'll carry on like it never happened. Worse drops may damage the drip tip.
That said, I carry nothing but the grand when I leave. But if I had to leave for 8 + hours, I'd put my 18650 flashlight in the car with a fresh battery so I could take it out and use it in my grand if necessary.
Or I might take a second grand. Dunno. Never had to leave for that long since I started vaping![]()
That is why I need one. seems like the perfect device for me.