1000 years. Celestia fears for her sister for such a long time alone, especially with Nightmare Moons influence over her. So she begs the stars for their help, and four answer her call. For 1000 years they will watch over her, until the 1000th year of the summer sun celebration when they will aid her in her return to reclaim her throne along side her sister. However the Mare in the Moon has other ideas, and still hasn't ruled out the night prevailing over Equestria forever!