I like 3.4v with my 2.0 LR cartos. Yes, you get a cold vape at 3.4v with standard resistance attys and tanks, but that's just a matter of matching the battery and the atty resistance to suit your own taste. 3.7v batteries deliver more current at the outset, but tend to drain faster than a regulated eGo because they are constantly producing more current on the same atty resistance.
The regulation in the eGo keeps the vape at the same level throughout the charge life, so you get a consistent vape until just before the LED flashes. Match the atty/carto with your preference and life is good.
That's probably true. I've never really tried high voltage but apparently I must like 3.4. I do like the 4.2 volt echo-e with some juices, but not all.