Take my word for it, I'll give you a lesson that you'll remember for a long while.

相信我的话，我会给你一个教训，你会记得很久。

youdao

For a long while he remained speechless.

他愣了半天没说话。

《新英汉大辞典》

She turned the matter over in her mind for a long while, but still could not come to a decision.

她忖量了半天，还拿不定主意。

《新英汉大辞典》

"There may be enough to eat for a while." he says, "but before too long there may be hunger."

VOA: special.2010.04.13

Yes-- for a while, but not for long.

是的，更快乐一段时间并不长久。

哈佛公开课 - 幸福课课程节选

"It will for a long time, at least while I am alive. And it is not just trucks and heavy machinery.

VOA: standard.2009.09.02

In front of the mirror she stared at herself thoughtfully for a long while.

NEWYORKER: Miracle Polish

For a long while it was about struggling to survive, struggling to get better.

WSJ: Designer Rick Owens's Paris Home | WSJ. Magazine May 2013

That moment is unlikely to result from a bold diplomatic initiative for a long while.

ECONOMIST: War and diplomacy in Syria