I've been working out since I was 13 so 5 years now. I'd honestly have to say that with a real routine like 5x5 I've only been working out for about a year. I've seen great gains in strength and size since starting 5x5 and modifying my diet. I do wanna look good tho so I add in certain iso movements for the parts of my body that are lacking size and shape.
At 18 I would say the routine is definitely not too much. At that age your body is able to recover much quicker, and adapt to new programs much better. Your still on your body's peak age for growth, use it while you can!