Alero headbolts ?

I am replacing a head gasket on a '03 Alero,and according to the manual they want new bolts used, can some one give me a good reason for this. I can't believe that with only 30,000 m that they would be...(not to mention the fact that I'm doing this job in the first place).

Thanks guys...................

The bolts are what are known as torque to yield! These bolts stretch slightly when torqued and when the torque is removed they will not go back to their pre-torque length. If you fail to use new bolts the old bolts will not hold torque and the head gasket will blow readily. You must use new bolts and you must torque them as outlined in the manual to make sure that the head gaskets seal properly.

Thanks alot !!!! I appreciate the response, guess i have to go back to the dealer and get'em....

Silly question, but if it's an '03 with 30,000 miles, why didn't you take it into the dealer for a warranty repair?