The fence post pictured is only 7 years old, this fence had many years of life left except for the breaking posts. Even pressure treated posts can be vulnerable to decay if not installed properly. Excluding the direct contact of soil to the post is an important part of a good installation. Decay is not the only enemy, when water is allowed to pool right where the post meets the concrete, caustic chemicals in the concrete are able to weaken the post.
I always make sure to create a small pyramid of concrete around the base of the post to route water away from it. this moves the exposed post a couple of inches above the grade of the surrounding soil as well. Most posts are 4×4 in size but, MBA Deck and Fence uses a special 5×5 post which is extra strong and resists warping too.