Depends on storage conditions. I have had some nutes in a controlled environment in my closet just chilling in a rubbermaid and no problems, but left some in the attic for one summer where it gets over 100 degrees outside here so I imagine it's much warmer in the attic and had a gallon jug of Clonex bind up somehow and sounds like its full of rocks now and no longer much liquid. My AN pH down went bad and became super potent. Even one or two drops in 5gal of water goes from 7.4 to 4.2 pH.

Also I know my Great White (benficials) has a best used by date on it.

Most likely it has to due with storage conditions and possible contamination (using the same dropper without rinsing in all nute bottles) but I have used some old nutes I had laying around (just not my go to nutes, but something better than nothing sometimes) for over 3 maybe 5 years old. But if it has stayed around that long most likely I don't prefer to use it anyway. Hard to throw away bottles 3/4 full that cost $80 (even if I don't like) when on a budget.

I guess when in question maybe try it on another outdoor plant with similar growth habits (not mj) and if it has adverse effects on this do not bring it back into the garden.