用在一般现在时，现在完成进行时，过去完成进行时。
例句与用法:
1.I've kept on thinking about that all the time.
我一直惦记着这件事。
2.In his job he's rubbing shoulders with film stars all the time.
他在工作中一直与电影明星有来往。
3.Then the scales fell from my eyes:he had been lying all the time.
我恍然大悟:他一直在撒谎。