User blog comment:Water Dragon Slayer/DREAM BATTLE CHRONICLES: FIRST MATCH!/@comment-11966702-20130717123030/@comment-33019320-20130717224752

Well, it depends on Magical power. Unlike Angel, Lucy can't open two gates at once as that would cause her to run out of Magic faster. However, since her Second Origin was opened, she's able to open two gate at once without tiring out easily. I also forgot to mention that some of the Celestial Spirits have a slightly different appearence during the battle although that might be just the Celestial Spirits wanting a change of style.