I bought some of that stuff and it's great, but apparently people keep in their cupboard for a long time. It's basically just water. I wouldn't drink water that's been sitting out for months.
Looking at the ingredients of a few brands, 'water' refers to the distillation process rather than the contents of the bottle. Most of them are essential oils suspended in alcohol with a little propelyne glycol to sustain the flavors. I think it would keep a really long time (1-2 yrs) if it's stored in a dark, cool place esp with an amber bottle. That said, you may get some off flavors due to oxidation over time.
If yours ends up being more than 50% water, I'd buy a super small bottle, fridge it, and toss it after a few months.
Ingredients: Water, Orange Blossom Essence.
Good points though. I guess based on that it could be up to 49 % alcohol. Wierd that it's not labeled like a spirit though.