你说的天荒地老我说的至死不渝
[nĭ shuō de tiān huāng dì lăo wŏ shuō de zhì sĭ bù yú]
Both phrases express the concept of 'till the end of time,' but they differ in nuance; while you might talk of enduring until earth ends (you said till earth's destruction, I said until death will not separate). It reflects different depths of commitment towards a cause or relationship from the point-of-view of this individual.