Speaking as a Monster junkie myself (Ultra Paradise FTW!!), remember that this shit is medicine and not something to just reach for whenever you're thirsty. 400mg of caffeine in a day is where shit starts to get dangerous for healthy adults; a can of Monster is 140mg (or at least, the Ultra Paradise is... no idea if the other flavors have more or less), so even if you're sucking down a can of these every single day, you're fine unless you have some heart condition or taking in lots of caffeine from other sources.
...and don't forget to drink actual water. I think the kidney stone thing is mostly driven by dehydration.