Call me "Mr. Overkill."

I carry two tubes, one adhesive patch kit, a co2 pump and a frame pump, and of course a tire lever (one of those really good yellow ones plus the one on my multi-tool).

The two tubes and the patch kit are in case God decides to smite me with flats on my way to work. The co2 is in case I get a flat and it's real hot or I'm in a hurry. The frame pump is also to challenge God's wrath and because I'm cheap and co2 cartridges are 3 bucks a pop.

I patch tubes, but in the safety and security of my own garage - usually in batches when I have multiple punctured tubes. If I were independently wealthy, didn't give a rat's ass about the environment and lived next to a 24hr bike shop, I would not patch tubes.

I've never had a problem with patches. Some of my tubes with 4 or 5 patches hold air better than some of my tubes with no patches at all.

One thing I always do is fight the temptation to test whether a patched tube holds air by inflating it. Before I inflate a patched tube, I put it in a tire on a rim. Then I inflate it to max psi and check it the next day. If it is still at or near max psi, then the tube is as good as any brand new tube out of the box. I prefer to have my patched tubes on my bike and my new, unpatched tubes in my bag.