对于这个问题阐述一下我个人的观点:首先,您上面所提及的英文例句中在我看来没有一句是定语从句(非限定性)。
1.The fire lasted for 5 hours, during which time everything was destroyed.
2.I will never forget the day, on which time I first met you.
3.He will put off the picinic until May 1st, on which day he will be free.
4.I told them the reason, for which reason I didn't come.
5.They went to London, in which place they lived for 6 months.
问题出在哪里了呢?which 的词性上。绝大多数人认为 which 在这里是个关系代词,我对这种看法并不认同,我认为 which 在这里就是个指示限定词,如:this、that 等,跟定语从句(非限定性)丝毫无关,而是介词短语作状语仅此而已:
during which time (作状语表时间)
on which time (作状语表时间)
on which day (作状语表时间)
for which reason (作状语表原因)
in which place (作状语表空间)
在此之前也有老师回答过诸如此类的问题,都以非限定性定语从句作为最终解答,在此我保留个人意见。