donkey's years很長一段時間。這個習語最早的說法是donkey's ears，為同韻俚語（rhyming slang），以與years押同韻的donkey's ears來比喻時間，後來才改為donkey's years。這是因為驢子很長壽，且用years更能點出「時間」的概念。
看看老外聊天時怎麼用donkey's years：
Molly: Blake? My God! It really is you.
Remember me? I'm Molly.
Blake: Molly! I don't believe it! I'm so happy!
Molly: I was pretty sure it was you when I saw you from the back.
Blake: How are you? I haven't seen you in donkey's years.
Molly: I'm doing fine. How about having dinner together?
莫莉：是布萊克嗎？天哪！真的是你，記得我嗎？我是莫莉。
布萊克：莫莉！太不可思議了，我真高興！
莫莉：光看到背影，我就非常確定是你了。
布萊克：你過得好嗎？我好久沒看到你了。
莫莉：我很好，一起吃頓晚餐如何？
donkey's years例句精選：
I've been a vegetarian for donkey's years.
多年以來我一直是個素食者
She's been there donkey's years.
她已在那兒待了好多年。
He introduced me to a friend he'd known for donkey's years.
他把我介紹給一位他已認識多年的朋友。
You could once get a glass of beer for ten cents; but that was donkey's years ago.
過去人們用十美分就買得到一杯啤酒，不過那是很久以前的事了。
拓展學習：
long-winded 冗長的
extended 長期的；延伸的
eon 極長的時間
coon's age 很長一段時間
a month of Sundays 很長的時間
in a snap 順刻之間