When I first started vaping, I looked at an e-cig as an entire component. You had a 901, which consisted of a 901 atomizer (and cartridge) and a 901 battery. Period.
As I started to vape, though, I realized that they really were separate components. For example, you can use your 901 atomizer with a USB passthrough battery. The battery plugs into any available USB power source, whether it be your computer, your house electrical current (with a cheap wall outlet/usb adapter), your car cigarette lighter (with a cheap cigarette lighter/usb adapter), or even with a portable battery pack (like the Kensington).
Once I got to that point, I realized that the 901 atomizer could be used with other types of batteries so long as the batteries were in a holder that worked with the 901 atomizer. So, for example, you can use a 901 atomizer with a Screwdriver, basically a device that uses non-ecigarette type batteries to give you a longer, more powerful vape. And, of course, there are many other such devices out on the market that use a 901 atomizer (either as its default atomizer or as a possibility with the purchase of an adapter)--the JantyStick, the GG, the Silver Bullet, etc.
So if you like your 901 atomizer and the flavor it provides but you don't particularly enjoy the short battery life, it's time to start exploring the options. (The cheapest option is the usb passthrough battery.)