There should be mutual give and take and if, over a sustained period, it's all one way, you need to distance yourself.

But that might be because no one has tried to get him out that way for any sustained period.

But she has not been outside for any sustained period during the day - without drastic consequences - for almost a decade.

After such a sustained period of hot weather, the resulting thunderstorms are expected to be unusually powerful.

No one yet knows if free schools work over a sustained period.