很高兴为您解答如下：
for +一段时间不一定用现在完成时,只要这个句子的谓语动词是延续性的,什么时态都可以用.
比如：I'll be away for some time.
He once worked in Janpan for 3 years.
也可以参看下面几道高考题：
1.--- I’m sure Andrew will win the first prize in the final.
--- I think so.He _______D____ for it for months.（2008江苏卷）
A.is preparing B.was preparing C.had been preparing D.has been preparing
2.He __B___ football regularly for many years when he was young.（2008天津卷）
A.was playing B.played C.has played D.had played
3.We first met on a train in 2000.We both felt immediately that we ___C___ each other for years.(2008辽宁卷)
A.knew B.have known C.had known D.know
主要根据基于目前情况下所想表达的时间
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