I would not necessarily look for something to be bad, but simply the steering pressure may be set too high. If you reduce the steering pressure via the relief valve on the steering gear, you will see an immediate change in the current draw of the motor.

Just dropping the load by a couple of amps, below the rated load of the motor should be enough to ensure the motor lasts. Also make sure you carry out periodic inspection and replacement of the brushes before they have the oppurtunity to damage and stick in the plastic holders.