Welcome to TBN .
Are you useing OEM belts ? Is the tension is set to mfr's specs ? If you replaceing with automotive type belts they wont last , they stretch too much , way to elastic IMO . You can also use the A n B type machine belts Gates with green strips .
Also check for burrs , misalignment ,improper tension, pulley wobble , proper belt.
How is the condition of your pump ?