That cannot go on forever, and meanwhile the clock ticks.

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The problem with the tablet market is that it cannot go on forever.

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Mr Westerwelle said Germany was in Afghanistan to defend its own security - "that is why this mission is right, but it is also right that it cannot go on forever", the Associated Press news agency reported him as saying.

BBC: Germany's Merkel makes unannounced visit to Afghanistan

All of the historians involved in the debate over decline agree that the age of American Imperium cannot go on forever.

BBC: Is the United States an empire in decline?