So being ruled by an actual immortal deity is defenseless?
I'm pretty sure in that 1000 years there must be a few clashes and crisis, but none of them was dire enough to use the Elements. Besides, the Elements only used four times (luna twice, discord twice), and all of them was to defeat some immortal beings, if it's about to defeat some slumbering griffon army or diamond dogs marauders, I'm pretty sure the Royal guards will be more than enough
Just my two bits