When drum brakes are the only type of brakes used on vehicles or trailers, don't expect their brake shoe linings to last as long as the brakes on machinery equipped with disk brakes or a combination of disk and drum style brakes. The actual life of drum brake shoes depends on what they are used on, how they are used and the quality of the brake shoe linings.
Longer than Disks
Many vehicles are equipped with front disk brakes and rear drum brakes. If this is the situation on your vehicle, expect the rear brakes to last about twice as long as the front brake pads. When stopping a vehicle, the front brakes do most of the work. This is only a rule of thumb since both brake shoe linings and disc brake pads are available in many levels of quality.
The length of service to expect from a set brake shoes depends on many variables, so a definitive lifespan or number of miles to expect is impossible to give. The important thing is to inspect the shoes or have them inspected regularly, and replace them when the lining wears down to 1/8-inch thick at any point.