@
79pmooney makes a good point about having two tubes. I might start doing that.
I carry one tube and a patch kit. Of course, I carry a pump and tire levers, too, plus some other tools.
I'm good at patching tubes, so I consider them fairly reliable. My tricks are to use more glue than you might think, spread it wider than you might think, and let it dry longer than you might think. To partially mitigate the drying-glue problem, I toss my punctured tubes in a bin and then patch them all at once every so often. I also use a big can of glue at home. I try not to use the little bitty tubes of glue. I now have a new routine of checking my tool kit every so often, and if my glue has been opened, I make sure it's still wet.