Commercials are often put to the boar at 8 months. I leave my GOS until a year old, so they're well grown and not trying to grow piglets inside them at the same time as still growing themselves. However, as I understand it, most commercials average 2.3 litters before going to cull and mine manage 10 or more.... The maths just doesn't add up for me but no doubt there's an accountant somewhere that can put me right on why the commercial route makes commercial sense.