One more question ... Do you find that manual or automatic
batteries are better? So far, I have just used automatics, but sometimes it takes a lot of sucking to get them going ... is that normal?
New buyers tend to want a small, automatic model with a tobacco flavor liquid refill, but experienced owners usually prefer a larger format model with a manual switch and a range of exotic flavors. This is why people buy new hardware eventually, and why an upgrade path is one factor worth considering.
Auto models have no push-button, they have a pressure-sensitive switch inside that reacts to air being drawn through. This turns on the atomizing heater coil and vaporizes the liquid. These models are easy to use for a beginner as they work the same as a cigarette. The auto models are more vulnerable to damage by a liquid leak, though, as they need an air channel through them - and sooner or later you will kill a battery because of this. There may also be restrictions on the drag length or number per minute, in order to try and maximize battery life. These restrictions can annoy experienced users, who may want to take long drags.
Manual models have a tiny push-button switch on the battery. They are sealed and therefore less vulnerable to leak damage. They have better control of the draw, since you can pre-heat it or switch it on for as long as you like. At first these may seem awkward to newbies - but it only takes five minutes to get the hang of.
The only difference between the two types of battery is the switch function - they can be swapped over. If you bought an auto e-cigarette, screw on a manual battery and now it's a manual. If you bought a manual e-cig, screw on an auto battery and now it's an auto.