I patched one on the seam last summer when it was Sunday, the bike shop was closed, and I didn't have a spare tube. It's still going strong. Wouldn't recommend it, though. I now carry a spare just in case.

Last year it was recommended to use heavy duty tubes (for my cruiser). They're a lot thicker and more expensive. After getting a puncture I patched it but didn't put it back on the bike. I don't see how a thicker tube is better than a regular one. If something penetrates the tire and tube, it's going to penetrate a thick tube, too. Perhaps they're more reliable in rough use such as mountain biking.