1)自从什么时候以来：That has changed since I was here.
I haven't seen her since last week.
这两句话的翻译很清楚：从我来这里以后变了很多.从上星期开始我就没有看到她.
It has been many years since I enjoyed myself so much last night.
翻译：直接翻译：从我昨夜玩那么开心,已经有很多年了.
间接翻译：我已经很多年没有那么开心了.
这里与延续动词关系不大,主要是句子的表达方式.