as long as 有两层意思：

1. 跟......一样长（指距离或时间长度）。例如：

This line is four times as long as that one. 这条线是那条线的四倍长。

You can keep my book as long as you like. 我的书你要借多久都随你的便。

网友的第一句，就是这个用法，说明居住时间之长，跟我记忆力所及一样：

I had lived with them for as long as I could remember, but I was not really sad to leave.

据我记忆所及，我和他们住在一起很久了，但我离开时并不是很难过。

去掉比较的部分则是这样：

I had lived with them for long, but I was not really sad to leave.

2. 用作从属连词，引导条件从句，as long as 带有假设意味，意思是“只要；如果；若是；在...样的情形下”。

网友的第二句便是：

You can go out, as long as you promise to be back before eleven o'clock.

只要你保证十一点前回来，你就可以出去。

又如：

You can watch TV as long as you have finished your homework. 只要完成了作业，你就可以看电视。

As long as you have passed the previous three relevant practice game, we can end the confrontation between rivals. 只要你通过了前面三关的练习赛，就可以对决最终的对手。

As long as you come, I am happy. 你只要来我就高兴。

Troubles fear me as long as I don't fear them. 我若不怕困难，困难就怕我。

as long as 引导的从句，还可以省略与主句相同的主语，然后用分词：

As long as going into the reading room，you should keep quiet. 只要进入阅览室，你就应保持安静。