As time increases, the angle increases and we can ask, "How long does it take for the particle to come back to the starting point?"

这个角度随着时间在增加,我们会问,"质点需要多长时间,才能转到起点"

耶鲁公开课 - 基础物理课程节选

How long did it take you to come here?

你到这儿花了多久？

How long实战 - SpeakingMax英语口语达人

On any given day I can feel great, but I never know when the pain will come or how long it will last.

CNN: Sickle cell patient refuses to let disease define her

Channelled up and down Crete's mountain canyons - veritable wind tunnels - these stiff breezes are known to locals by individual names, depending on from where they come, how long they stay, and what gifts they bring with them.

BBC: Seductive southern Crete

How come it takes so long for my smartphone to connect to the Internet so I can look up a phone number?

FORBES: 94% Of Americans Blame Their Computer