I don't know how long my crying jag lasted.

我不知道我一阵大哭持续了多久。

《柯林斯英汉双解大词典》

Sorry, I don't know how long he will stay in Xinjiang.

不好意思，我不知道他要在新疆呆多久。

youdao

I don't know how long I can hold out.

我不知道自己能够坚持多久。

youdao

What's important about the construction of St. Petersburg-- I don't know how many of you have ever been there; I haven't been there for a very, very long time-- this city is not like Moscow at all.

那么修建圣彼得堡到底有什么重要的意义呢,我不知道你们之中有多少人去过那儿,我并没有在那个地方逗留过很久,但这座城市和莫斯科完全不一样

耶鲁公开课 - 欧洲文明课程节选

But I don't really know about how long it would take people to hack, like, the general firewall

但我不知道人们具体要用多长时间才能穿过防火墙，

理想是当密码专家 - SpeakingMax英语口语达人

I held off for a very long time, but I just got mine a month ago. And now I don't know how I live without it.

我拖了好长时间，一个月前才买的。而且现在我不知道离开它该如何生活。

没有智能手机活不了 - SpeakingMax英语口语达人

"I've had a slab of bacon in the freezer for I don't know how long, " Forgione says.

WSJ: New Yorkers boldly flout law to keep pigs

Worst of all, we have to postpone our plan to have a baby for I don't know how long.

CNN: The Cost of a Pegged Dollar

We had certainly known for I don't know how long, but we've known that this was going to Rules Committee today.

WHITEHOUSE: Press Briefing