Multiple tasks

Can I do this in my Tasks add-on...

public function define()
  {
    $this->add(120, 'getPhotos');//get new photos every 2 hours
    $this->add(360, 'getPhotosetsListing');//transform these into galleries every 6 hours
  }

Or am I limited to one? (I only as as the second task only fires if I comment out the first.

Ta.