You know that even native speakers can not know a word and might need a dictionary at least a couple of times in a book, right? :)

I would say for Chinese to finish a book without a dictionary it took me about 9 years. Of course that was a really easy book, probably about middle school level.

Ive been doing Chinese for almost 20 years. While I confess I haven't read that many books all the way through, I've read thousands of newspaper, magazine, and jounral articles.  Nowadays it's much harder to complete a whole book even in my native language. I would say reading nonfiction stuff for the popular reader doesn't absolutely necessitate looking words up, although my personality and my profession (translation) compel me to look them up anyway. Fiction is a little harder because I have much less experience with it. Again, if it's popular fiction its's usually considerably easier to read without a dictionary although somebody like Ba Jin can be read easily despite being considered literary.

@ Karl Franz
@Royal Shiny

I do use dictionaries for specialized books. When I read fiction, I don't look for the exact meaning of obscure medical, technical or scientific terms. I wouldn't recognize them anyway.

@Aficionado
@Murillo Costa

There was a time when I couldn't reach page 15 in any language and I had to buy a translated version. It does get better with practice.

@Alfonso

I found out that if I keep reading, I will encounter the same word many times and by the end of the book I won't need the dictionary so often.

I remember when I was just a beginner in English... On some occasion I had to read a book for a test at school, and I tried to read through the book without looking words up in the dictionary. But, of course, in the end I was unable to understand what was going on in the book...

So, actually, for me it wasn't until I was studying English at university that I could do without looking words up.