Dude every day. If you lived at my house you'd catch me playing the day away with Ruby, Gold, and Red all the time. I just can't leave those games.
EDIT: I don't exactly play them for nostalgia. I play them because I really enjoy them and pokemon kinda stops at Gen 3 for me. In fact, nostalgia is a factor that really never comes into play for me and I don't really see playing GBA games as "retro gaming". Even Red and Gold, and I know Red is pretty retro now, both games don't have any nostalgia factor for me. I just really like playing them and catching whatever pokemon I still don't have. For example, all this time I never had a Yanma in gold until yesterday.
Oh, and of course I always play FireRed. You have to add that to the mix.