What sort of failure are you experienceing? Are the spokes breaking at the elbow on the rear drive side?

Most spoke breakage is caused by insufficient spoke tension, or failure to stress-relieve and/or retension after a few hundred miles.

Perhaps the 'expert' who built your wheel is an expert for building wheels for lightweight loads, but not so good about heavyweight/high mileage. What is 'good enough' for a racer dude to use as a training wheel might not cut it for fully loaded touring through developing countries.