halo 3 double exp

hi guys just a quick question. i have only just got the legendary map pack (i know, way late) and so i can only now take part in double exp weekend.

my question is do bungie do this every weekend or just once every so often similar to cod4?

thanks for any answers.

I have only known it not be double exp weekend once so far, though I must admit I'm not a hardcore halo player.

You can always check bungie.net to see whats going on that weekend, they are really good at communicating with fans/players and are constantly updating the site.