I've had good luck with Elmer's Rubber Cement -- patches lasted probably 4-5 years.
Lost a can of Rema when it dried up over a summer. Trust me, losing a $25 can hurts more than losing a $3 tube that way.
I'm starting on my third summer with the
JoeTBM referenced. As of the late winter patching party, it's doing fine -- and no failures on patches glued on with it, either.
Of course, the key is good surface preparation on the tube. You've got to sand or scrape the mold release layer off the top of the rubber.