How long a stay did you have in mind?

你原打算待多长时间？

《牛津词典》

We can arrange time efficiently and know how long a single task will take.

我们可以有效地安排时间，并知道每项任务需要多长时间。

youdao

It was this, "Pretty thin--as long a dream as that, without any mistakes in it!"

是这样的：“这可不信——这么长的一个梦，居然没有一点差错！”

youdao

They saw Grant as a strong and silent soldier a great leader who had won a long and bitter war.

VOA: special.2010.02.11

Joshua Bolten had a long and a distinguish carrer in the White House in the Bush White House.

约书亚·博尔顿在布什总统,白宫办公室,任职时间长而且工作出色。

普林斯顿公开课 - 国际座谈会课程节选

So if you answer the phone, you'll be saving me from a long conversation that will last ten hours.

如果你去接电话的话，我就可以免于一段又臭又长的谈话的痛苦了。

Would you 实战 - SpeakingMax英语口语达人

People with ADD are terrible at estimating in advance how long a task will take.

NPR: Excerpt: 'Delivered from Distraction'

When there was a long walk or a long wait, she got a ride.

FORBES: Travels Down Under With Alice, Age 88

Using a lens with too long a focal length, for instance, makes the image appear flat.

ECONOMIST: Animation takes on a whole new reality