Immortal-ish Character's Dialogue

[trykynyx.livejournal.com]

So I'm doing a fun little side project involving Greek gods in the modern age and a certain pop star, but the specifics aren't really all that important. I was just wondering if anyone who wrote characters that have lived a particularly long time (vampire/god/robot/whatever) could give me their perspective on dialogue? Do you go for the "I Am Old And Speak In Archaic" thing or are your characters a little... hipper? I swung back in forth in the same scene and couldn't make up my mind... So, any ideas?