I have wondered about this myself. I have tried researching this, but I haven't found an answer from an official source yet. The only thing I found was that in a medical setting, they throw away open bottles of N after 30 days, because the anti bacterial seal is broken, and they can't use it. It's not because the N has gone bad. There are older posts on here where people have guessed that it would last anywhere from a few weeks to a few months after it was opened, but that isn't official. I don't know if anyone knows for sure.
If I opened the bottle and backed out at the last minute, I would have it tested if I waited more than 30 days before I attempted again. That would be the only way to know for certain how potent it was.
I have worried about the same thing. I mean there is already enough of pressure and worrying about overcoming SI and being able to go through with it without having the added pressure of opening the bottle and wasting the N. It's not like if you waste it you can just order more like SN.
There was an older post on here where someone said they decanted their N in another bottle several months beforehand, and he later successfully ctb with it, but I don't know.
