My LFS is having a big sale on Instant Ocean salt this weekend... $29 for a 200G box. That the lowest price I’ve seen for IO in quite a while and I’m debating picking up like 4 or 8 boxes, but that would probably be about a 1-2 year supply for me. I feel like as long as it stays dry the salt should last pretty much forever, but is there anything I'm missing or any reason (other than lack of space to store it) that I shouldn’t buy so much salt at once?