I've beaten both games twice. The first time, it happened over the course of 10 days, with a total of 80 hours over the two. I spent 10 days playing 8 hours a day of Golden Sun and The Lost Age. I don't think I've ever gamed that hard with anything else, ever.
Needless to say, I'm mega hyped for Dark Dawn. It's my most anticipated game. Even though Zelda is my favourite series ever, I'm still looking forward to Dark Dawn more than Skyward Sword. Can't wait.