Use corrosion resistant solid shafts only. Sleeves do not add strength to shafts. Sealed pumps should not need sleeves, unless you are using the type thet Frett and groove shafts. Make sure you have enough Net Positive Suction Head Available to prevent cavitation. Do not let air enter into the system.
Air comes in through shaft packing, flanges, and valves above the water line.
Vortexing, aerating the incoming liquid, and pumping the suction dry are other common causes. Replace wear rings any time the original specified clearance doubles. Pay attention to parts storage. Proper packaging can increase this life considerably. Many pump power ends are already rusted internally at the time of installation because of poor storage policies and no internal corrosion protection.