I'm sorry I haven't written to you for so long.

真抱歉，我这么长时间未给你写信了。

《牛津词典》

I found it a strain having to concentrate for so long.

我觉得这么长时间全神贯注挺累的。

《牛津词典》

We haven't had such a severe winter for so long, have we?

我们很久没有过这么冷的冬天了，不是吗？

youdao

They say their findings offer one reason why the custom of cursing may have continued for so long.

VOA: special.2009.08.18

because the government's expenditures are only going to keep the economy afloat for so long.

因为政府的开支就是要保持经济的长期运转。

担忧未来 - SpeakingMax英语口语达人

So it took a long time for the twenty books that we have to get settled on. And we'll talk about how that actually happened,also,still.

所以很长一段时间之后那27本书,才最终被确定下来，我们会谈及,那是如何实现的。

耶鲁公开课 - 新约课程节选

Some say gold-related shares, which have been unloved for so long, now look attractive.

WSJ: Rising Stock Prices Flash a Warning��Selloff Ahead?

Almost nothing else about the global economy has stayed so constant for so long.

NPR: After 200 Years, U.S. Remains King of Cotton

And why would Assange hold onto the documents for so long before publishing them?

FORBES: Is Bank Of America WikiLeaks' Next Target?