We eliminated the inner bin our our compost about eight weeks ago. The air gap between the thick wire and mesh bin channeled too much heat out.  Now we have just a 4′ diameter mesh pile full of wood chips, with a 24″ column of vegetable compost in the middle, and temperatures pushing 60ºC in the center.  Our system is to load the compost roughly every month, letting vegetable waste build up in 5-gallon buckets, and then loading 10-20 gallons into the pile at a time.  We shovel off the outer 12″ of wood chips, put vegetables mixed with paper & cardboard into the center column, and then cover back up with wood chips.