Batteries sold in walmart and crappy tire usually have 3 year warranty, and they will most likely die after 3 years.
Walmart battery 77-100bucks - life expectancy 3 years
OEM battery 200-250 bucks - life expectancy ..... well beyond 7-8 years.
My car is '03, still has OEM battery which is made in '03, my buddy has a '00 coupe > his original battery just died (so thats 10 years).
I totally recommend OEM battery as opposed to any walmart crap.
Just buy it from whoever sells it the cheapest.