Before you leave your home office, do a quick 10-second check. Look at the mouthpiece and see if there's any condensation. That's a sign of temperature swings. Give the device a gentle shake—if it sounds sloshy, the e-liquid is too thin. That's a warning that it could leak later.

Also, think about where you'll keep it. If you're going to be in direct sun for hours, plan to have a shaded spot. A small insulated pouch works, or even a zippered pocket in a backpack that's off the ground. Avoid leaving it in a car, even for a short errand. A car's interior can hit 60°C in minutes.