They are not meant to be the kind of stove that keeps you warm all night long. Though the volume of some of those large oval stoves has me wondering what kind of a burn I could get out of them.
15-20 is about what I have gotten too.
packable stoves are not airtight at all, they burn hot, and they burn fast. Main reasoning to bringing them seems like to go to sleep warm, wake up warm, dry gear, and cooking.
Really nice once the fall sets in and the nights get long, spending a few hours in the evening by a stove that is red hot is soothing.
Putting on warm socks and boots is really nice too