I've been interviewing people for more than twice that long. I started with the conversational approach, and it worked poorly. There are too many people that are good at talking about technology but bad at actually doing.

My mature interview style is a pair programming session on a specific exercise (the same for everyone). It's inspired by the "RPI" (Rob's Pairing Interview) from Pivotal (well, Pivotal of old days). There are no gotchas to it, it's not hard. But it's definitely programming. Because that's what I'm hiring for. Not talking.