I am going to save money（）six months.中间填哪一个介词

这个空可以填 in 或 forI am going to save money in six months.6 个月之内我会省钱 （比如你买了一个机器,虽然起初你花费了很多钱,但机器的功能会让你6个月之内把所花的钱省了回来.）I am going to save money for...为什么，during不行吗介词 during 在这句里不适用，正确的含有 during的句型是I am going to save maney during the next 6 months或I am going to save money during the 6 months I am living with my parents.I am going to save time during a six-month periodduring 有“一段时间” 的含义，仅用 "during six months" 是不对的，正确的表达方式是during a six-month periodduring the time 什么什么等等。我是加拿大人，英语是我第一语言，我也曾是英语老师。