Two i had last week from different vendors where shrink wrapped and both have exp 2015 on them, not sure if once they are opened the would be ok then but i would ave used them by then.
About two years is considered about right but I have found after a year the flavour changes, and not in a good way. Not had an 'off' one as such though, just not quite right. Longer shelf life can be obtained through proper storage as in somewhere cool and dark. Some folks store them in their fridges and even the freezer
I had a nightmare with a certain very well known imported liquid going off. I bought a 100ml bottle and by the time I was about 40% through it it tasted disgusting....really bitter. Then someone suggested keeping it in the fridge. Since then I've continued to buy the same brand of liquid and it's stayed fresh to the end. I get through 100ml every FIVE weeks though ;-)