Hey guys, sorry I missed so many posts here.
Mike, Thomas got it pretty much exactly right. No surprise there! The CFB doesn't hold up too well to abrasion, but it lasts indefinitely in the flame path. I find that I don't beat up my firebox as much as one would expect, these stoves are cool and easy to load so you don't bang wood into them like in a typical box stove. As such, I'm on year three with my core and while there is visible wear in the firebox it still isn't an issue. When it's time to replace, a couple new small cheek boards can be easily inserted into the firebox and I'm good for a few more years.
The performance benefit is worth it to me to deal with a bit of abrasion wear. The firebox is sized such that one could line it with firebrick splits, or your kiln shelf, to eliminate wear issues, but I've found that I don't care for how that performs. It creates poor burns and hot, hard loading conditions. That's a decision that one can make on their own once the stove is built.
As for building the whole core out of Mullite, I suspect performance would suffer. That said, I'm just wrapping up a firebrick version of this core to offer with the Tiny Cook Stove Plans for those who can't or don't want to source ceramic fiber board. The efficiency will suffer a bit, but they are still fantastic cook stoves. So, I suspect you could use the mullite if you preferred. If you do, I'd love to hear your experience.
Ju, the aluminum stoves are just skins over my ceramic board cores, so the core plans basically are the aluminum stoves. I'm happy to help with skin details if you decide to build one. I don't have any package deals at the moment, but I really like the ideas for books and video series you propose. I will work on those! Thanks for the kind words.
Simon, you are right it's a fine line. I suspect that if you build just the stove body with no bench you would have a small cook stove mass heater that would heat your space for 8 hours or so after a burn. Hope that helps.
Thanks all for the support!!