The only long term side effects that I am aware of is increased blood pressure and heart rate. These things can be reversed if you stop taking the medicine. There may others but they are unproven. These drugs have been around a long time and have been well studied.
As long as you don't have high blood pressure, you shouldn't have any health problems from most ADD drugs.
Some people say there are other side effects / consequences. I disagree. I'd ask your doctor.
Well, you don't outgrow it as much as you learn how to compensate for it. It is a "for life" kind of thing. However, you may find jobs that don't require the complete attention that school did. Things like a smart phone with its alarms, and notes can be very helpful. And, of course, the more organized scheduled you are, the better it is for you.
Many adults are able to get by with their meds on an "as needed basis".
The main way to prevent health issues is to make sure you understand what ADD is and what it can do to you. Anxiety and depression seem to follow those that don't understand this.
Adult ADD sites like "Jeffs add mind" can be very helpful in dealing with ADD as it is full of advice from those who deal with it daily. The site is -
http://jeffsaddmind.com/for-first-time-visitors
Hope this helps. Please post if you have any more questions. Best wishes.