Like somebody said. New bolts are supposed to be replaced if the FSM says to. Some say they are Torque to Yield, I say they are just cheap. I have used old bolts for Hundreds of thousands of miles and dozens of clutch changes. Older cars used bolts of a better quality IMHO and I clean and loctite them.

BUT

if I were to race it or beat down on a modified engine I would use new ARP bolts plain and simple.

By old I look at anything older than about 85 as old.