Yes, getting too dry can harm a guitar though at 45 years without damage, I wouldn't be too concerned. Conscientious humidification is most important when a guitar is new. The wood in a new instrument will still have an optimum moisture content from the maker. If it dries too quickly, damage may occur. Of course if your guitar had been humidified since it was new, sudden drying might still damage it. As it is, humidification or lack thereof will affect its playability from season to season but otherwise you're probably OK.

Were it mine, I'd humidify. I'd try to get it "normalized" then keep it in its case with a humidifier when not being played. I keep Oasis humidifiers in all my cases the whole year around. I live in the Midwest where we run air conditioning in the summer months. That means the indoor air is dry then too. Since we play a lot of outdoor concerts in the summer time, I've found that keeping my guitars humidified cuts down on tuning issues when playing outside.

My friend and master repairman Marty Reynolds in St. Paul, MN, makes humidifiers and sells them here ==> http://mnluthier.com/merchandise.html#hbox . They are also easy to make and I think he posts the details for making your own. I made some and use them through the winter in addition to the Oasis units.

      - Mark