The lesson here, more likely, is that even though these novels are long, it is rare for the same sentence to be repeated exactly multiple times. It is also highly likely that the sentences that are repeated are extremely short because the longer a sentence is, the less likely it will be repeated (unless deliberately). In addition, the repeated phrase might appear heavily in one portion of the book and only be repeated a few times after that, if at all. However, the deliberate reiteration is enough to cement the phrase in a list like this. So eightbitsamurai, not that I've read hunger games or care to, I wouldn't be surprised if the introducrions of katniss to all the other characters and game contestants might include a repeated query, "how old are you?" Certainly I expect it would come up when she is being interviewed etc. It doesn't surprise me that all these sentences seem very banal because you wouldn't really want to repeat anything interesting a ton of times, it would get boring by the 4th time you read it.