It sounds like something was splashed onto the post to cause that to happen (perhaps the fluid inside the battery? It is corrosive.)
Batttery posts last a very long time if none of the corrosive materials of the battery get on it. I have a 12 year old car and mine are not corrosive at all (neither does our four year old car). In this case the brand and model don't make a difference, the care of the car does.
You should make sure that any corrosive materials are taken off that battery post. Here is a way to do it that works for me:
Mix 1 tablespoon (15 ml) ofbaking sodawith 1 cup (250 ml) of very hot water. Dip an old toothbrush into the mixture and scrub the top of thebatteryto removecorrosionbuildup. You can even dip the ends of thebatterycables in hot water to dissolve anycorrosionon the cable ends themselves.