The bearing needs to be pressed in... I have put them in with a hammer and a bearing install tool too, on my car in my driveway BUT I wouldn't do that on a customers car because thats not the proper way to do it. The bearing needs to be "pressed" with a even load to be installed properly not drove in with a hammer. But regardless I would start looking at maybe a hub/spindle problem.. I've never seen a bearing go bad that fast that many times....