From everything I've read, the best way to store is in a closed box in the fridge. As for shelf life, I don't think anyone can say for sure - I don't know of anyone who's had an opened bottle of liquid for a year or two and then tested it.
I've had a couple of bottles stored for 3 or 4 months and they're fine, but that's not very long. Maybe this is a good question for the general forum - a lot of people are stocking up now.