Once you are really done with a tube keep it around and cut it up to make rubber bands or to use under clamps so they don't slip, etc...
This inner tube failed at the valve stem:
http://bp3.blogger.com/_P7uBKyp9qxI/...06-18-lock.jpg
I did the same thing to another MTB inner tube that had a pinch flat I hadn't repaired yet, for my sis-in-law's chain when I gave her the bike. I could have patched it, but I decided to cannibalize 4 feet of it for a chain sleeve, then use the rest for rubber bands.