from my experience, beer lasts a few minutes once its in a cold glass in front of me.

jk
it depends on how cold its kept. in a fridge i think it should be good for 8-12 weeks. kept out of the fridge... not long. probably a month.
by the way, i went to spagnols and bought these 2L bottles of home brew beer.
it looks like this:
http://www.brewsuppliesdirect.com/in...iter-kits.html
they sell it for under 3 bucks! thats equal to a six pack. all you do is put a yeast capsule inside, and screw on the new lid. wait 10 days, fridge, and its ready.
awesome!! im gonna drink it today, let u know how it turns out. if its good, im gonna buy like 5 of them next time.
the ultimate lazy man home brewed beer. zero equipment needed.