100 years ago 10 hours was lifespan for an airplane. Now we know how to fly and design airplanes pretty reasonably, a plane needs to be able to last a regular human lifespan to not have a question of is it strong. I say no questions asked for 70 years is about right. When it becomes a vintage airplane, I will accept restoration needed. In the 50s when Cubs and Champs were cheap and stored outside, you also recovered the plane every five years replacing the rotted wood or steel tubing. Every five years the plane was gutted. I would have to cut the covering off every year for piece of mind if I believed in using GG. If you are allergic to epoxy, build aluminum and rivets.