The packing nut has to be tightened continually to stop water leaks.  This leakage not only causes a loss of coolant but is also messy.

The wear that occurs on the impeller end of the shaft and wear of the boss in the head causes considerable endplay.  This endplay in the shaft generates misalignment of the fan pulley and can even cause wear on the pump by the pulley.

The original design of the front bearing (fan end) will cause premature wear of the shaft.  If not replaced, it can cause the shaft to break and do considerable damage to the hood, radiator, etc.