If I have a tube that seems like it's getting too many flats or patches fail after a year or two I figure that something's wrong with the tube and replace it (has to be the tube, it couldn't be me ) I'm riding on tubes with five or six patches though, and haven't tossed a tube in several years.

I don't throw them away - I cut up old tubes and use them for elastic strips. Affix heavy duty velcro to the ends for example and that comes in handy.