她指出前十年辐照牛肉在全国很多杂货店都有出售，但这并没有持续多长时间。
She pointed out that irradiated beef was offered at many grocery stores nationwide at the beginning of the decade but it did not last long.
但良好的关系并没有持续多长时间。
但这个估计没有说明整个过程需要多长时间。
But this estimate gives no clue about how long it will take.
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