How long is Holden's journey in The Catcher in the Rye?

The story doesn't say but when Holden asked her she replied that she is old enough to know everything she does

through context clues, it can be inferred that Sunny may, in fact be around the same age as Holden, so she might be a 16 or 17 year old prostitute. Holden mentions that she talks like a teen would say