How long does aloe vera juice last?

I bought some pure aloe vera juice a few months ago, but I'm hesitant to continue using it as it does not have any preservatives in it. I can't find any date on the bottle and it's hard to find any information on-line about this. How long does aloe vera juice stay unspoiled? Would you be able to tell if it went bad? I took a sip of it and it tasted a little more tart than I remembered - is that a sign of it spoiling?