User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-76.219.133.10-20130605154611/@comment-3146930-20130606014713

When Percy is talking about his "short miserable life," you have to consider that Percy is only 12 in that story. Rick Riordan's role at the camp is Camp Scribe, meaning that he records what the characters are telling him (which is why everything is past tense). If Percy told the Camp Scribe the tale of his quest, his life would only be a short 12 (almost 13) years. Even if Percy told the Scribe all this after The Last Olympian, he would still only be 16 at the time; still a short life.

The Heroes of Olympus series however is told from a third person-limited point of view, so no scribe. This means that anyone could theoretically die, as everything is real-time instead of past tense.