He paused enough to consider the options but never so long as to lose the initiative.

参考译文：他停顿了一会儿权衡/考虑那些选项，但并没有久到丧失/失去了主动权。

解答如下：

以上属于so+adj./adv as to do sth引导结果状语从句

Would you be so kind as to do me a favor, please?  

你会这么好心地帮我一个忙, 好吗?

Will you be so kind as to do it for me?  

请你替我做这件事好 吗 ?

She is not so foolish as to do that.  

她不至于愚蠢到干出那样的事来.