While it's true that nicotine has a shelf life...if suspended in PG and kept frozen, it can be kept for 10 years or so. Or so I've heard from those who seem as though they ought to know. Maybe even longer. Some claim "indefinitely". I don't know. I'm not worried, really. I may never get all the way through my stash in my freezer since I figure I'll eventually end up at 0 nic. Maybe even sometime this year. Or not. I've got about 500 ml. in the freezer now. I only have to use 4ml in a 60ml. bottle for my 3.5mg. DIY juice. So it'll last awhile. It comes out to 7,500 ml. of prepared e-juice. Thassalotta juice!