I live where it's really thorny ... so for a while (October - December) I was getting a flat just about every ride. So, I had a good stock of tubes and patches. Since most of my issues were single punctures they were easily patched, but I often needed to submerge the tube to identify the hole.
So, I'd install a new tube on the ride, then patch the damaged tube at home later. And, I only patched tubes once. Another hole meant the trash for me.
In my bike kit, I carry a tube and a patch kit (just in case). I had two flats one ride ... but my buddy had another tube.
Scott
Incidentally, Stan's No Tubes eliminated this issue for me! Haven't had a flat since I started using it, and I'm riding cheap tires and no liners.