I recently discussed this elsewhere..cos i bought some cheap out of date stock, now coming up to a year passed it's sell by date....and you know what, it's perfectly fine! Better maybe..since it's had all that time to steep.
Some apes in here have got ejuice thats several years old...and they've had no probs with it! It does depend on the ingredients used..as some might 'go off' perhaps..but generally most are fine. The only issue is, as the juice gets older, the nic strenght may lessen a tad..but that's about it.
So buy it, and vape it mate!