When do I throw out the old tubes and tires that I purchased long ago and never got to use? I have a bunch of tires and tubes that have been stored in a cool storage room, but with a water heater. Several of them might be up to ten years old, and most look good, but are there chemical changes unseen by me that should prevent me from riding on them?

My biggest mystery is the set of Conti Touring tires on the tandem. We once rode the last couple of miles of a 60 mile day on a completely flat rear tire. I couldn't tell from the captain's saddle and my wife, who is a non-cyclist, was clueless. Anyway, the tire looks perfect, and rides perfect. It is ten years old. Hmmm. Any thoughts? TIA.