I've used this mix for a couple of years now and it works. You don't have to worry about storing it mixed up; it will be fine. I have a rubbermaid tote
with a lid on it. I usually mix up a tote full at a time and take it out to my sites. I have four or five sites and I put out 20-25lbs at a time.
It is just easier to keep the minerals and salt in the bags. Who wants to
try to move around a 200lb trash can full of mineral. Keeping it in the individual bags just makes it easier to storeand move around the garage for me.