*#&$* just typed a long response and got it zapped.

Cliff notes version- All tubes have a spine, and it never changes it' s orientation. It' s true that the graphite and epoxy matrix will degrade over time, but consider fishing rods... I have 20 year old fly rods that have been cast hundreds of thousands of times, and the spine is still in the same place and the rod is still going strong. Were the graphite to " shift" in any way, the arrow would shatter on the next shot. It' s a myth that spine goes away.

I know this from owning a fishing rod business making custom rods for the last 17 years. In the fishign industry, spine is a really big deal and well studied. Bottom line, just mark your arrows and look for flyers. Discard any flyers, and put it out of your mind. Those arrows will not go bad for thousands of shots unless they get dinged.

One thing to think about- many of the epoxies used to make arrows degrade in sunlight. Never leave your arrows or your bow in the sun any longer than it needs to be.