On all tours, long or short, I carry a patch kit and a pump.

On a long tour, I bring a replacement inner tube. On a short tour, or if I am going out for just the day, I may or may not carry one.

But going forward, I will always bring an extra inner tube. I just experienced a rare failure: the nut on the presta valve snapped off while I was inflating the tire, which rendered the valve useless. The only solution: a new inner tube!

The moral: Unless you are OK with not being able to cycle on a cycle tour, always carry one or more replacement inner tubes.