If belts keep breaking I would check the idler and spindle drive pulleys. The drive pulley maybe worn or corroded and the belt may be riding too deep or being cut by corrosion. Idler pulleys may look good but if the bearings are worn, it will cause the belt to ride on pulley edges causing jumping or breakage. Finally if you are using after market belts they may be slightly shorter, which will increase belt tension. Also, after market belts may have a different pitch the OEM belts. One or a comination of these may be causing breakage.
