On a note regarding batteries, if I strictly want to run it at 3.7 volts, then I would just need one 18650 for the GGTS?
Does anyone know how many hours it lasts for in general?
It's a really difficult question to answer because it depends so much on how you vape, and how many breaks you take etc. A constant and VERY heavy vaper can usually keep going on an 18650 for 15 or so hours. A less frequent vaper who takes breaks may last double that.
Check out my calculator at:
http://www.e-cigarette-forum.com/forum/gg/42435-gg-vaping-time-calculator.html