The only comment about warping came in the context of why ceramic cats break up. The context was that in some stoves (other brands) the cats are not supported as well and/or are attached to parts of the stove that will cause torquing. This may be the result of extreme conditions in the stove (i.e. overfire) or even in some cases simply uneven heating of the metal in the stove. At any rate, if a ceramic cat is bent/twisted etc (especially while very hot) it will crack and/or break up more easily. Makes sense to me. The implication of the conversation of course is that the cats in the FV are better supported and not subjected to these strains. Now taking this bit of information and applying it to your question I would have to guess that we don't have to worry about it. Looking at the physical layout of the steel cat it looks like it should not have a problem with warping - they have the familiar honeycomb design that the ceramic has and they are rather thick so I'm not sure what axis they could warp on (i.e. mechanically it appears that all surfaces are very well supported). I'm sure time will tell (nobody to the best of my knowledge has burned one for 5 years yet) and of course WS has a reputation to uphold and I see no reason that they wouldn't stand behind it if a problem were to pop up later.