User blog comment:Miskos3/Fairy Tail Chapter 385: The Celestial King vs. the Underworld King, Review/@comment-24734283-20140523231005/@comment-24.86.98.90-20140525012353

Not to mention, Lucy summoned two of her more "costly spirits," Leo and Aquarius, when she had three spirits out; it's likely if she uses some less powerful spirits, she could sustain 3 spirits in the future.