Larry Dean Olsen's book _Outdoor Survival Skills_ has a couple of pages on keeping fire. The one that I remember best was sort of like an oversized fat cigar, with a core of wood coals, wrapped in increasingly-thick bark, finished off with a wrapping of fairly thick bark strips. If I remember correctly--and it's been a while--he may have said something about how long this setup would last; the idea was to stop, start a new fire, and prepare a new fire-carrier whenver one's old one was on the verge of losing its viability.
As I think about it, for your more-stationary setting, you might do best just digging a pit and building a sizeable fire in it, and then experimenting a bit with how much air needs to be let in to keep it going. I know they used to make charcoal in commercial quantities back in the 1700s by building, semi-burying, and lighting piles of wood; the wood would burn to charcoal over several days' time. I think that process required some high degree of watchfulness, lest the fire either go out or roar into full force. Also, if you use the "pit" method, take care to keep kids, etc., from trying to walk across it.
Good luck!
