定语从句中That,which,where 等的用法

定语从句中That,which,where 等的用法
我看了一些参考书有关于定语从句的用法,但是有一点我不明白,
书上说：“先行词为表示时间、地点的名词时,关系词不一定都用when或where.如果关系词在定语从句中作主语或宾语时,就要用关系代词WHICH或WHAT.”这句话是不是绝对的啊,是不是遇到这种情况都要这样处理啊?如果是那么这书上有几句话我不明白.
1、This is the factory that/which we visited last year.
2 I won't forget the time that we spent in the countreside.
以上两句是按上面的意思的,可是下面一句为什么还是用WHERE?
this is the house where i lived two years ago.