A repair using high-strength concrete would last a lot longer than wood, even if it's pressure treated. Concrete likes water, gaining strength over time. Research has shown that 50-year-old concrete is stronger than identical specimens which are only 40 years old, as long as adequate moisture has been available for hydration of the Portland cement particles. Water is the nemesis of wood, and the porch's roof overhang probably isn't enough to keep the area dry during inclement weather.
Just make sure to take the load off the column with temporary supports before removing the damaged material.