Sometimes the settlement of an estate can drag on for years. And sometimes researchers assume the amount of time it takes to settle the estate is because the estate is a vast one that heirs spend decades fighting over in court. Not always.
Smaller estates, perhaps even a farm that was just big enough to support a family, may have stayed in probate for an extended time for another reason: waiting for all the heirs to become of age. If that estate takes fifteen years to “settle up,” look closely at all the heirs. There may have been one who reached the age of majority around the time the estate was closed out.