许你终生只为天长地久
[xŭ nĭ zhōng shēng zhĭ wéi tiān zhăng dì jiŭ]
The expression '许你终生只为天长地久' means ‘Pledging my whole life for eternal love.’ This signifies a devotion to lifelong love or fidelity and expresses commitment towards lasting and endless affection despite challenges that may come along the way.