Throughout the undying rule and lifespan of an alicorn, the lives and deaths of innumerable ponies would flutter by like waves crashing in an endless ocean, a price Twilight and Cadance could see behind the smiles and love their mentors always carried. A price they themselves knew they would face when invited to sit by them on the throne, to shape and operate the kingdom for millennia to come.
A price they never bothered to embrace till one night, when the elder princesses would invite them to pay witness to the last breath of life Equestria would ever know to a fragment of its fertile soil, no matter how tiny or insignificant it may appear.