OEM batteries are made better and will typically last around 6-7 years from what I have seen.
Batteries are made different than they used to be. Instead of having a solid lead sheet they have really thin lead foil that wraps around a paper insulator many times around. The problem is these are much more likely to flake and the deposits create a short in the bottom of the battery.
My battery of choice is Deka. I have never had one that lasted less than 5 years, and I have had many of them. You can keep those wal mart batteries. Only last a couple years tops.