Coil resistance has absolutely nothing to do with battery life in a regulated mod.
Well.. the lower the resistance someone uses the higher the watts they tend to use and the lower the battery life generally, and more juice....
You're not going to drive a 0.5 ohm coil at the 10 or 12 watts you're likely to use for a 1.8 ohm coil.. 100 3sec puffs at 20w will drain twice as much from a battery as 100 3sec puffs at 10w...