There was a very old nirvana shirt I bought second hand. I wore it until it literally dropped. During pogo (or moshing) and I stood there half nude at the concert. That's punkrawk.
ATM I don't haver very old pieces of clothing. It seems to me that the quality dropped drastically during the last few years. After wearing a shirt or a pair of trousers for more than one year you may kick it into the garbage can.
So the oldes piece is about 2 years old.