Yaar this is too early to change brake shoes. Did you change front and rear set or only one set? Usually the front brake shoes last much longer than the rear brake shoes. So I think you changed your GD's rear brake shoes. Still, it is too early. I changed my CD 100's rear brake shoes and drum rubbers at 25,500 km (around 2.5 years after purchase date). I sold my CD 100 at 28,381 km and never had to change the front brake shoes.
Either the quality of GD's brake shoes is pathetic or something caused its brake shoes to deteriorate before time. Please have this investigated what caused them to be changed so early.