I have hundreds of wooden spools of thread, many dating back to the 40's or before. Silk, cotton, rayon, nylon and combos. You all say to keep them, that they are collectibles. They are only collectible if there is a market for them...which there isn't that I know of.
I do not use the last layer that has been in direct contact with a wooden spool because of the acid and I do test it for breakage before starting, otherwise, if the color is right, I use it regardless of age. Never had a problem yet. For heavy use, show or heirloom quilts I use new threads.