I had problems a couple of years ago with the cherry frames (the outer frames, not the bellows frames) of my accordion twisting a bit in the very dry conditions of the Yankee heated home. This resulted in air leaking around the gaskets.
This year, I have placed an instrument humidifier in the case, and I indroduce water occasionally. This is not a scientific experiment as I won't have before and after photographs of the reeds, but so far the wood seems happy.
One Louisiana accordion builder on this forum recommended never adding humidity to an accordion's environment. I understand the concern, but I'm not sure someone from Southwest Louisiana can really understand how dry things get: when it's 5 degrees F outside, static sparks fly in the house! There is no way that the environment inside my accordion case is going to become more humid than the 80% or 95% relative humidity conditions under which the instrument was constructed (unscientific presumption, I know).
Anyway, I'm not recommending this, but I will report on the condition of my reeds when Spring rolls around.
This may make a difference with an internally mounted microphone. The vibrating reed is right up by the orifice providing an overriding level measured in db. Reflective waves do eminate from these holes as well, but are unnoticable to the majority of ears. The blend of harmonics from all stops open and playing in octaves really swamps out any reflective waves.
I age my violin woods for two years. The wood is supplied air dried as well. I stopped building guitars 10 years ago. Playing the bowed instruments and many acoustic guitars (not all!)change the tonal response and in almost all cases, for the better.