How long can you hold your breath?你憋气能憋多久？

He says he'll do it, but I'm not holding my breath. [=I doubt he will do it]他说会去做那件事，但我深表怀疑。

“She promised to pay me tomorrow.” “Well, don't hold your breath.” [=do not expect her to pay you tomorrow]“她答应明天给我付钱。”“唉，别指望了。”