Is it safe to store Aquaforest reef salt mix for a few weeks at a time?

[Rob Lion]

That makes sense. What if I turn on a wave maker inside the container a few times throughout day? I've read that stirring the mix will also lead to quicker precipitation, right?

Sadly no, the best thing you can do if you are needing to store fresh saltwater is I believe to use a tightly sealed container as @Waterjockey does. Its being open to the air that allows evaporation / pH change to take place.