pretty sure it depends on the type of beer and what you consider "life".
A few examples; hoppy beer like american pale ale can lose a lot of the hop character after a few months. A strong abv beer should last longer than a less strong one, and wheats are meant to be drank young.
If you use plastic bottles, I've heard it won't last much longer than 6 months.
If it's in glass, i've heard of beers being opened 10-15 years after bottling, and although oxidised, and have lost all hop character and carbonation, it's been infection free and drinkable.