Move the seal closer to the bearings. Split seal designs are a logical choice because most come with a stuffing box extension gland that positions them next to the bearings. A support bushing or sleeve can be installed in the end of the stuffing box to minimize the effects of unbalance, vibration and shaft whip or wobble. Various materials are available for these support sleeves. Check with your supplier for availability in your area.
Open impellers require frequent adjustment.
If you use this setup, a cartridge seal is your best approach because impeller adjustments can be made without disturbing the seal face loading. Split seals can compensate for the initial impeller setting, and split seals mounted on a split sleeve easily compensate for movement caused by temperature growth or impeller adjustment. Closed impeller pumps need to be disassembled and have the wear rings changed when the clearances become excessive. If you are fortunate enough to have adjustable wear rings on your pump, only an outside adjustment will be needed. The pump won't have to be put out of service.