Highbeam, you seem to be hung up on this one factor. Why beat it to death? However, just how can we explain why someone has gotten 18-20 hour burns. I've even heard of longer burns. As you well know, burn times are relative. There are just too many factors involved to state that a particular stove will get x number of hours. For example, I've read that the Fireview can't even get a decent 8 hour burn! I've kept that a secret from our Fireview and it knows no better so happily gives us much longer burn times. Of course, it depends upon what wood we fill it with too....
Can you post a link to the thread where someone is getting 18-20 hour burns consistently.