I have varius sticks, sheets, shaped pieces of balsa, some bass and spruce sticks that I bought 30 years ago. stored in such a fashion to keep them straight and flat. Perfectly fine. I have a couple of planes that old also. Covering is done for, but the airframes themselves are just fine. Glue joints wood be suspect before the wood. They were sealed well from oil penetration by at least 2 coats of thinned epoxy.. Bodys and wings stored to prevent wrapping. Bodies flat and wings on their leading edges, never stood up on an end.

Ken