Thanks for all the comments and perspectives. Pretty interesting to see a nearly 50/50 split on this poll so far.

Like many others, I carry a new tube on rides and reserve patch jobs for doing several in bulk in the garage over a beverage. Also like many others, I keep unsalvageable tubes for other uses such as cutting into small rubber bands.

The location is also interesting - I can confirm that this puncture was caused by a fresh goathead in the tire. If I hadn't removed the thorn myself I would have thought that the previous patch job might have been faulty.

For the sake of experimentation and amusement I've sanded the area down a bit and threw on a new patch. I've clamped it overnight and I will report back to see how it holds up after mounting on a spare wheel.