I really don`t know the answer to this, but I think there is a strong possibility that it may be OK. Of course it depends on storing conditions.
Sake stores frequently sell bottles that are 1 year old, so I doubt the life of sake is only 6 months from bottling. I am sure the life is very short once the bottle is opened though, as there is always a warning on the bottle to drink it as soon as possible after opening.
Although the storing conditions are different, there is also aged sake (just like wine) sold in stores. These bottles can be more than 10 years old.
Sake stores frequently sell bottles that are 1 year old, so I doubt the life of sake is only 6 months from bottling. I am sure the life is very short once the bottle is opened though, as there is always a warning on the bottle to drink it as soon as possible after opening.
Although the storing conditions are different, there is also aged sake (just like wine) sold in stores. These bottles can be more than 10 years old.







