I think that early in the burn those secondaries will light off but just not stay active as long. Black glass is a sign of either poor fuel or an air leak and, of course, the two combined. Oh how I wish we had our Progress right now as folks are learning how best to run these stoves.... I'll wait though. As for the 16 hour burns I do think folks are not completely understanding that. It sounds as if folks want a 16 hour burn throwing lots of heat and I highly doubt that will happen. In order to get long burns the wood has to burn slow and we also have to realize there are only so many btu's in any type of wood we burn. For example, popple can burn very nicely when needed but I doubt one would even get a 12 hour burn in a Progress with this wood. Granted, that is an extreme example but if folks expect a 16 hour burn each and every time they fill the stove than I suspect there will be some very unhappy people. This is why I hate to see those claims of x number of hour burn in any stove. Shoot, I can get over a 12 hour burn in the Fireview but when the outdoor air is cold, that simply is not feasible. Yet, it is possible to get a 12 hour burn from that stove. If someone bought a Fireview expecting a 12 hour burn all the time, I'd tell them to buy a different stove! Also, I fear there are many on this forum who are taking what some posters state and think that is the norm. It is not and many will learn how to run this stove and run it well but perhaps not overnight. It simply will run a bit different than some other stoves. We still have much experimenting to go and that is the real reason I wish we had our Progress now so that perhaps we could help a few others. But we will get it in time.