How many times must one read a text in order to appreciate it like a painting or a song?
How many times must you look at a picture or hear a song to appreciate it?
Sometimes once is enough, sometimes twice is too many and you begin to lose appreciation. Sometimes you never get it, sometimes you get more each time. Depends upon the work.
Nabokov has said that the second time you read a book is actually the first time. He theorized that the first read-through is simply you getting acquainted with it. I can link the essay where he talks about this, if you want.