I have not used a black bear, but have seen a lot of 118's and that type of stove did easily provide overnight output - it uses the cigar (front to back) method of burning, as opposed to the whole load being on fire at once - this can result in longer burns given the same size firebox. Jotul 118's are being used by the tens of thousands in Norway - where it is cold, cold, cold.
Although Elk claims long burns with an Intrepid, this is not my experience or that of my customers (not the claim of the manufacturer) - The intrepid and the 602 were the two smallest stoves that our shop sold....maybe followed by the Jotul 3CB....
When we are comparing these, we should compare them in the same installation with the same chimney,etc. I saw a lot of people get overnight burns on 602's, but that would not lead me to tell you to buy one for that use. I don't doubt that the 3CB or Intrepid can do the same....but in my opinion, it is difficult. Stepping up the Castine, Black Bear, Resolute (in VC line), mid-dutch, and many other models will assure a longer burn. BTW, what is the cubic foot of the black bear firebox?
One review on the black bear - there may be more - rates it a 2 (1 is best, 5 is worse), but does give all the good and bad points in the comments - this review seems fairly truthful:
https://www.hearth.com/ratesingles/rate1744.html
About 10 intrepid reviews there too, everything from love'em to hate'em, but one person states a 6 hour burn is the top. I agree with that (in general).
We can't forget you said "secondary heater" so a lot of this stuff may be unimportant to you.