An 18650 provari lasts me over 12 hours chain vaping.... and I WAS a 2.5 pack a day smoker. No wires to get tangled, broken, or wrapped up in things as a mail carrier is not just driving, he is also constantly moving. My 2.5 has been run over 4 times and fallen off my deck 36 ft up in the air, it still looks good and fires like a champ.You completely missed the central requirement which is:
This is why the usb passtrough and the DRV were brought up.
If pass through is something the OP is considering I would recommend wither the provari with pass through attachment or and MVP as it also has a rugged form and the Las through on both will immediately remove itself from the mod, in an event, that the device gets tangled keep falls while the mail carrier is working.
If something can go wrong it probably will, just the way I think, especially under what will obviously HEAVY usage, and the best mod for HEAVY usage is the provari, they've stood the test of time, and right now is the most economically advantageous time to get one, with the extension.