Ddubyou
Why don' t you just take them in to a pro-shop and have them tested. Most good shops should have a spine tester, especially if they also deal in traditional gear. Might be a small fee involved.
No one has come up with a reliable, repeatable way to actually measure spine- but it' s a myth that it goes away. Take good care of your arrows, and you' ll never need to worry about it.
Thats not true at all. Any of it. Repeated use will effect spine. Take a piece of sheet metal and bend it back and forth a few times, will the metal weaken - of course. Same idea with arrows.