Composting materials can take varying amounts of time depending on the exact conditions. A good way to tell how well its working is to see how hot the matter gets. Bob Flowerdew, you know the regular on gadrfeners qustihon tme..., gets his so hot your hand can't withstand being buried in it. Aeration, ratio of carbon to nitrogen rich input and the presence of living creatures (such as worms) all effect the efficiency of a composting. My design would benefit from an increase in size, facilities for rotating its contents, addition of Red Earthworms (which would in-turn require bedding: newspaper, sawdust, hay etc) and selecting suitable plants such as Squash, Pumpkins and melons.A ratio of carbon content 25:1 of nitrogen by weight is best.