"But how long can you stay in the house?"—"I don't know. It depends."

“但你能在这屋里待多久？” — “不知道，这要看情况而定。”

《柯林斯英汉双解大词典》

But how long will it continue?

但是这能延续多久呢？

youdao

But how long will credit be cheap?

但是信贷会廉价多久？

youdao

But no one has the answer to how much market share Bing will claim from Yahoo or Google in the long term.

VOA: special.2009.07.17

If we weren't so pressed for time, I kinda wanna see how long we could get away with this before it gets awkward, but that, in fact, is an infinite loop t hat's hopefully deliberate.

如果有时间，我想看看,我们需要花多长时间解决这一问题，事实上，它是我故意,使用的无穷循环。

哈佛公开课 - 计算机科学课程节选

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

But how long can that survive given Wales' failures to make the fixtures a competition?

BBC: Tri-Nations aura arrests Wales development

Technology is hot, but how long this happy investment cycle will last is anyone's guess.

FORBES: How Fast Can You Learn?

But how long before these constructions that make prescriptivists cringe are considered proper usage?

BBC: Are language cops losing war against 'wrongly' used words?