ZJ asks: What's the meaning of "night after night"? Is it the same as "day and night"?

My comments:
Yes, "night after night" is the same in meaning as "day and night".

Both expressions are used to describe things that are happening continuously for a long time. For that matter, they are the same as "day after day", "day in, day out", "day by day" as the case may be.

As the case may be because even though they are all similar in meaning, they are not always interchangeable, each having its own subtleties. That's why things like these are best learned in context, which, in turn, allows you to put them to use correctly. Only when you can put a word to use correctly, can you claim to have had it under your belt. Otherwise, you can't say you've "got it", even if it appears as simple, mundane and harmless as night and day.

Let's take a few examples.

If you have a day job, you may say: "Day after day, I have to do the same things." Yawn.

On the other hand, Yao Ming in America is mostly on nights (NBA games are mostly scheduled in the evening). Therefore, "night after night, he (Yao) has transformed into everything people feared upon his ceremonious arrival four years ago, delivering 30 points and 15 rebounds on nights now as easily as a man walks down his driveway for the morning paper" - The time is Yao, by Adrian Wojnarowski, Yahoo! Sports, November 21, 2006.

"Day after day" describes situations that are always the same old, same old, without changing. If there is change, you may say: "Day by day, my English improves." That means your English is getting better gradually, little by little.

If the situation lasts for a long time, use "day in, day out": "She cooked and cleaned day in, day out for forty years" (Longman Dictionary of Contemporary English).

If something happens continuously and all the time, use day and night: "He was attended by nurses night and day" (Longman). Here, "night" is put first only because the nurses' jobs at night are considered more wearisome to perform than during daytime.

In this Jazz oldie (Night and Day sung by Billie Holiday) that I'm listening to, the night is long and lonely for Lady Day:
... Night and day you are the one
Only you beneath the moon and sun
Whether near me or far
It's no matter, darling, where you are
I think of you
Night and day
Day and night...

Zhang Xin is Trainer at chinadaily.com.cn. He has been with China Daily since 1988, when he graduated from Beijing Foreign Studies University. Write him at: zhangxin@chinadaily.com.cn, or raise a question for potential use in a future column.