I read somewhere that Flax seed does go bad. The stuff I buy is only 4.00 for a flour small bag and that last weeks, plus the full seeds are pretty cheap in the store. I'm personally a thrower awayer type of person and would not chance eating old food. Maybe you are more adventuresome than me and like the challenge, but I hate upset stomachs. I like your suggestion better of throwing it outside and seeing if it will grow.
Let me know if your milk machine will make rice milk. That stuff is expensive (of course I like the expensive stuff) and would love to know how to make my own.