On my first long ride, I prepared and bought two continental tubes because they were expensive and seemed reliable. I even practiced at home changing the tubes, just in case. Had tools, good lezyne pump and two tubes with me.
At the farthest point in the ride, my first flat ever. No problem, since I prepared. I followed all the steps I prepared for at home, easy. Just as I want to unscrew after pumping 120 times to get good pressure, the core comes loose and the entire thing deflates.
Kept spirit up, tried again, 120 strokes later, same thing. Literally did this for 6-7 times over the course of about 1.5 hours, until it finally stayed on. Very happy at that point.
Attached the wheel, continued riding, 15 minutes later, the new tube is now also flat. Another hole. The same thing happened with the other continental tube, but this time the valve core exploded and flew away somewhere. I got home because a friend came to help with tubes.
Since then, I only buy michellin aircomp or airstop tubes. Actually haven't had a flat with them in months, solid tubes.