There's little benefit to continuously using energy drinks. You quickly develop tolerance to the caffeine (in a matter of days) and developing other problems (particularly GI issues, lack of quality sleep, irritability, etc) is more the issue than it being particularly dangerous.
The people who die "because of energy drinks" usually had existing heart conditions (sometimes undiagnosed), go for days without sleep, take it on top of prescription drugs (often stimulants), and/or consume those energy drinks like they are soda or water (but without drinking water or staying hydrated). It's usually a combination of more than one of those factors.
2 energy drinks a day isn't a huge deal, especially if they are sugar-free and you don't consume coffee or other caffeinated beverages as well. But it's not a substitute for sleep (with caffeine's half-life, it will interfere with sleep if you have an energy drink within hours of when you are supposed to sleep), and if you aren't taking care of your nutrition it will contribute to poorer health overall.
I've consumed energy drinks for about 10 years. My advice is to not drink them if you don't need to. They aren't significantly worse than drinking soda or excessive large coffee drinks all day (which a lot of people do), but if you drink them all the time they don't energize you, they will keep you awake and you'll feel like crap without necessarily realizing the cause immediately. Plus, you can possibly get mild withdrawal symptoms like headaches for a few days when you stop.
I regularly drink teas (black, green, white, ginseng), coffee, and sometimes yerba mate. I don't drink energy drinks every day, and often I go weeks or a few months without them. For me it's only when I need to stay up during the day (I normally sleep during the day since I work the grave shift, so for me all nighter = all dayer) that I have more than one, and even then it's always sugar-free nowadays and increasingly rarer that I do.
So really if you don't "need" to drink energy drinks, don't. But if you want to and are aware of the downsides, it's very unlikely* to kill you or otherwise pose a significant health risk if you don't over consume them.
* Disclaimer: I'm not a doctor, nor am I giving you medical advice