I already commented on this issue stating that there exist quality differences between various IFBs, but now I'm thinking that they should not be used in the wood flame path.
Two vendors/manufactures that I inquired about IFB use in flame path said it was OK, but at the same time it's rather obvious that they are not intended for wood flame path:
1. IFBs are rather new invention, established in industry in the 50s.
2. Industry uses natural gas, propane or electricity to melt, crack, kiln fire.
3. If wood is burnt in biomass power stations or incinerators - high alumina hard bricks are used (I read some paper), because amount of fluxes and detrimental substances is high.
My electric ceramic kiln is lined with IFB-26, but it's electric and only I converted it to propane and propane exhaust is super clean compared to wood and I use it maybe 10 times per year only, so I may not be able to notice any deterioration.
I just read that IFB/propane kilns may have longevity of 1-5 years in high use environment. High use for ceramics firing would be once per 3 days, because cooling to less than 50 C (safe for glazes) takes me around 40 hours. For quick raku firing (objects are removed hot from the kiln) firings could be more frequent with much more thermal stress.
Masonry heater will be probably fired for let's say 4 months, so with one fire par day it's 120 firings - equivalent to once per 3 days kiln use schedule. However the fuel is wood with chlorine (bricks don't like it) and various fluxes. Also the temperature in properly built riser is equal and turbulence much higher than in a kiln.
So it looks like IFBs in wood flame path are really being tested by us. I'm really curious about performance of IFB risers built by others.