Well- at the risk of being the odd man out- here it goes- I've done research on this topic & I've found the following- all bolts have a "stretch" value. The question is- during assembly- does the bolt enter into this "stretch" ?

Older engines used 3/8" or 7/16" head bolts & each cylinder had 5 or 6 bolts surrounding it and the cylinder head was cast iron- the same material as the block so the expansion rate was the same. The torque values on these bolts didn't come close the the "stretch" value. New engines use only 4 bolts around a cylinder and the cylinder head is aluminum. Given the fact that the head bolt now has to deal with 2 new forces- less total clamping force per head and clamping 2 materials that expand differently, they have designed the torque value of head bolts to purposely enter into this 'stretch" zone. The head gasket, cylinder head & head bolts are now part of a matched set designed to expand & contract independently of the engine block.

The new way to torque cylinder heads gives a more uniform torque value throughout the entire head assy, that is it's purpous. It's not an indicator that the torque value is going to enter the "stretch" portion of the bolt.

With all that said- the choice to re-use or re-place head bolts lies in the person who ultimately will have to spend either the time or the money to re-do the job again.