That’s probably if the temperature difference is s extreme like coming from a freezer and into a sauna.let’s not kid ourselves,it is only wood and I don’t think a layer of cardboard will make any significant difference.It’s like the whole tonewood for electric guitars nonsense.
In truth, I think the fear of something cracking is that the finish on a guitar will crack ... and that wouldn't look good on a $2,500-and-up guitar. In fact, on some low-priced electrics you get a good number of finish cracks for one reason or another, and maybe that has to do with the heat in the factory construction. Still I recommend the 24 hour thing. In fact, as I think I said, that advice/warning is very prominently put on the outside of the box at Martin. But it's up to the new owner.
