现在进行时较好，因为后面有for some time .但如果强调现在放弃，并不再进行，陈述得只是过去的事实，那么过去时也是可以接受的。
We urgently need to conduct a survey about real estate market.
过去进行时表示过去这一段时间一直在讨论，一般过去时表示过去讨论过，所以过去进行时好，We were discussing this question for a long time.
用现在完成时更好，We have been discussing this question for a long time.
用现在完成进行时。 We have been disscussing on this program for a long time.
This plan has been discussing by us for very long time.
现在完成进行时
We have been discussing this plan for a very long time.
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