Here's a feature that often matters more than raw capacity: how fast the device charges. If your battery dies midday, being able to get 20 minutes of charge for another hour of use is a lifesaver. Look for devices that advertise rapid charging (often 1A or higher).

Passthrough is another underrated feature—it lets you vape while the device is charging. That's perfect for desk workers or anyone who hates waiting. Not all devices have it, so if you're often near a USB port, it's worth checking.

These features can make a smaller battery feel like a bigger one. A 400mAh device with passthrough might serve you better than a 600mAh one that takes hours to recharge.