Wow - interesting thread.
I have a question though... I always thought wax was a polymer - isn't it? As such, shouldn't wax's physical properties/behaviour be more similar to the behaviour of other polymers?
I'm really thinking back here, but IIRC polymer chain length had a lot to do with how a polymer behaved. Shorter chains meant a softer material, longer chains meant a stiffer material. Does aging of wax result in additional chain linking over time? This would cause it to become harder and perhaps more brittle. Since reheating causes wax to melt, I'm guessing heat also breaks the chains down into smaller "links," which "re-link" on cooling to some intermediate length which restored pliability. Just some thoughts...
I enjoyed the steel discussion - haven't heard anyone even mention the word "martensite" in 15 years - took me back to college days and my "Ferrous Production Metallurgy" class (among others).
Steel has another interesting trait that hasn't been mentioned here directly yet - it undergoes a ductile-to-brittle transition at low temperatures. We demonstrated this in lab using charpy bars, a charpy impact tester, and liquid nitrogen. Chilled bars broke cleanly in half, while room temperature bars usually just bent or tore part-way through. Though liquid nitrogen made the steel extremely brittle, steel can become noticeably brittle even at more "reasonably encountered" temperatures like those that might be encountered in Winter in the northern states or Canada. Thought you might find this interesting.
"If it ain't broke, I'll break it!"