I worry about the humidity issue as much as anyone who loves his guitars. I lived on the dry prairies with a long heating season. Even then, I never had an instrument damaged by low humidity. The furnace had an inefficient humidifier attached which crusted up very quickly from the minerals in the water. The house humidity in winter could not possibly have been suitable for solid wood guitars. However, at that time, I kept a damp-it in the guitar body and that seemed sufficient. I certainly played for an hour or two at a stretch, and removed the damp-it for the duration, but the instrument went right back into the case, the moment I was done, even if just for a bathroom break. When finished, the damp-it was refreshed (not so wet as to drip) and the guitar went back into the case for the night. Yes, I was anxious about possible damage, but no such thing ever occurred. However, the nature of the guitar's built and conditions under which they were built may play a factor. At that time, I mainly played instruments built in Japan, such as Sakurai and Kohno. Also, my teacher had a Ramirez 1a, which received similar care, and he had no problem with damage.
Presently, I do live in coastal climate with, thankfully, short heating season and no home humidification. For most of the year, RH in the home is between 45 and 60. My guitars were built under similar RH in a shop on the coast. Yet, it is scary how fast the humidity drops when the furnace runs for a few days, as it is doing now. During this snap of sub-zero, the RH as dropped to 35 already and, if prolonged, it will easily go into the 20's. Contemplating this anxious moment, I prepared and installed my home-made case humidifiers. (This is a simple device of medicine vial with perforated lid; damp sponge inside; and attached in the case interior with velcro.)
I do play for an hour or two and then store the guitars in the case. The cases I'm using now seal tightly, so I become equally concerned that the humidity in the case might become too high. There's nothing one can do about worry!