For overnight burning, load the heater at least half an hour before going to bed. Only turn the air supply down to minimum once all the wood is charred (about 15-20 minutes) to avoid creosote problems. Most heaters should still burn for eight hours without difficulty and you will have far less creosote problems than if you fill the heater and turn it to slow-burn straight away. However, long periods of slow burning will always produce more creosote than burning on medium or high. It will probably take you some time to get the "feel" of operating your heater for long periods. You might even find that once you have a good lighting method worked out and you house is well insulated you don't need to burn overnight except on the coldest nights.