You might not kill them instantly, but anything less than 2.5ohm will reduce their lifespan significantly.
A 2ohm LR carto on a 180mah 510 battery will cut it's cycle life by 1/2 to 2/3.
You might want to look into a passthrough, but not a 5V passthrough. Litecig has a passthrough with a 10440 battery built in. It supplies a steady 4V to the handpiece, which looks just like a 510 battery, but isn't.
5V is a lot of voltage for a LR carto and will probably burn it out in pretty short order. With the 4V battery passthrough, you aren't drawing amperage from your USB port, so it's safe to plug into your computer.