I know many people have the notion that you'll never be as good as a native speaker in a foreign language. A few of us have the audacity to aspire to native-equivalent performance in our second languages and even fewer strive for native-sounding pronunciation. Even if we are delusional, I think for those that really want to be extremely good in another language, there is no reason that we can't expect to be able to read like a native.
For languages with alphabetic scripts or even phonetic scripts, reading as well as a native may not sound like something that would be questionable. All you need to do is put in the time and even if you don't feel like looking up unknown words, eventually you'll get a pretty good idea of what most of the words mean.
But for Chinese and Japanese (any others?), reading is quite a challenge even at the advanced stages of learning. I haven't much experience with reading Chinese, but I do for Japanese. So let me just talk about reading Japanese.
Japanese has two phonetic syllabaries as well as Chinese characters called Kanji. The phonetic syllabaries, Hiragana and Katakana, are about as different as uppercase and lowercase characters in the alphabet. They just take some practice reading and eventually it becomes no problem.
Kanji, on the other hand, is the problem. Many Kanji have 2 or 3 readings, while the most overly used characters have lots of readings. Looking up words with characters you don't know requires you to write the characters on a dictionary device of some type or another. Then, you'd better make a note somewhere because you don't want to have to look it up again.
Really, it is quite exhausting, so I don't recommend trying to look up every word you come across. It's better to wait until it comes up a second time. So if you remember seeing it before, then look it up. Statistically, I think this makes sense. The least frequent 1 or 2 percent of words are likely only going to show up one time in your reading. These 1 or 2 percent words may make up half of your unknown words, so you can save yourself a lot of trouble.
To illustrate what I mean, let's say your book has about 10,000 unique Kanji words, and let's say you know 4,000 of those already. That leaves about 6,000 words you would have to look up while reading the book if you were to go through the trouble of looking up every word. But if 3,000 of those words are only going to show up in the book 1 time each, you would forget even having seen them by the time you see them in another book. So it's not worth making the extra 3,000 look ups and notes.
OK, of course I'm just making those numbers up, but you do want to save time and trouble, don't you? The number of words that fall in the final 2% is about the same as the first 98%.
I have a book on Chinese vocabulary frequency. It tells of a Chinese corpus by BLI Press that has 1.8 million characters, contained 31,159 individual words. Out of those, 16,593 of the words occurred 3 or more times in the corpus. 8,000 of those words make up 95.1% of the text.
So, you see, if you look up every word in your reading, you are in fact, wasting a lot of time.
How many hours does it take to reach the same reading level as a native? I don't know! How long would it take you to read 1.8 million characters in Chinese? You probably don't know! But we're too far along to stop now. So let's keep going!