Comic books were for kids 5-10 years old...
Emphasis on were. Just two cite a few examples, take a look at Sandman, Fables, or Watchmen.
Mostly correct, a few did target a slightly higher aged demographic, but safe to say you should be moving on from comics by the time you are a teenager.
When I was a child, it was controversial for children to be allowed to read them. The church I went to condemned them as an evil influence. However, my mother told me I could read anything I wanted. Her only stipulation was that I go to the library every Saturday morning and check out four books. So every Saturday, I would be taken to the library and made to choose four books. Many times, I just grabbed anything at random off the shelf just to placate her but would at least leaf through them. What this did was expand my horizons considerably.
I did read a lot of comics as a child. My parents didn't have a lot of money so I'd borrow them or pick them out of other people's trash. At one point, I had several milk crates crammed with "Archie", "Richie Rich" and just about anything I could get my hands on. When I was 12, I was heavily into MAD magazine and other knockoffs like Cracked and Sick. But by then I was reading at a college level and I soon got bored with comics.