While it should work fine, it probably won't pass code inspection. For most non code welding it's not the big deal some make it out to be.
I did vacuum pack some extra rods in retort pouches I expect to sit on the shelf for a while. Some new rods are supplied that way so it should be ok. But this isn't for code welding, just some expensive hardfacing rods, that were only available in a large quantity. I have yet to open any of those and see how they held up. Otherwise I try to buy small amounts, so I always have fresh rods. For things like 7018 if they have been stored open, there is a procedure in the datasheet for baking them out, but I've never tried that. Too easy to just buy new ones.
Long arc, short arc, heliarc and in-the-dark!