I have been reading and most of the "adverse" effects seem to be in regard to large doses. Especially large doses in people not used to it. If one builds a tolerance to large amounts of caffeine be it from coffee or energy drinks what are the long term health effects aside from the dependence/withdrawal symptoms?
The long term effects of dependance is that you feel "dependant" on caffeine, which leads to the answer of the next part of your question which is; when you are dependant on something and you do not satisfy that dependance you get withdrawal symptoms.
I don't think there is any "longer" term health effects, although some studies have shown that people that drink 3-5 cups of coffee and have a lower incidence of diabetes and cardiovascular diseases. Obviously its not ideal to be dependant on any substance, although 3-5 coffee's a day is probably not classified as been dependant on it.
Paul Chek (who has one or two articles here) has a pretty interesting theory about this
If i recall correctly, he says basically caffeine speeds up everything, metabolism, brain, and given that we have a limited time to live, it speeds the process of getting old as well, since we're proceeding faster.
I neither agree nor disagree but food for thought for sure.
Energy drinks do include chemical's in it so stick with organic natural coffee or something, at least it contains antioxidants.
Whether there are long term sides effects from significant caffeine intake (particularly coffee) is probably largely individual. Some process it quite well and easily while others don't. Even drinking 6-8 cups of java a day, spread out throughout a twelve hour period say, I personally don't have any issues with sleep, energy levels or anything else. To me, whether I drink lower caffeine tea or have a 16 ounce Starbucks dark roast, it's a very mild stimulant that cause no (apparent) issues. And it's great just prior to a workout!
By contrast, if my own sister has a single 8 ounce cup of Joe at 3 pm she can't sleep till late at night. From what I understand we have different stomach enzymes and body chemistry that either allows caffeine to be filtered out of the system by a certain period or we don't and it keeps circulating. Strictly a genetic luck of the draw it seems.
As for the health benefits there are plenty to drinking coffee, IMO. In addition to the previously mentioned possible cardiovascular benefits, it has been published in medical reviews that coffee drinkers, who consume about 4-6 cups (about 8 ounces each) a day, have about a 50% chance or preventing certain cancers, in particular colon cancer.
Note: Just make sure that the java is organic, if at all possible; it's been reported that coffee is one of the most heavily sprayed crops (I like Newman's Own Organic Special Blend to name one, and it runs about $8-10 a pound in most supermarkets), and it goes a long way going organic.
As for longevity and lifespan, it's worth noting that two of Europe's biggest coffee consuming nations - namely Italy and Greece - have one of the longest lifespans (and quality of life) around the world, and they both have significant coffee consuming populations.
So in short, if it doesn't keep you up late at night and make you jittery, enjoy. Compared to other things (and other stimulants, respectively), coffee and caffeine is way back on the concern list, and I consider it one of life's best vices, and one that probably does you a little good in return.