We aerate 162 acres every two weeks about 9 to 10 months out of the year. The ground is the black clay. We are pulling cores about 6" deep on our best attempts, 4" is more typical. The fields are used for soccer, so they are very compacted. We do not aerate just for the turf, the aerating helps with the impact attenuation for the players. This helps with making the ground softer for the players when they fall.
If it was my aerator I wouldn't change them out as frequently. Our mechanic doesn't want to repair them, it's easier for him to replace them annually than make the repairs. We could probably go every other year and get the same results with minor repairs to the spoons.