So it was less than 21 minutes above 12,500. Ummm... What about the PIC? There were no FARs that weren't complied with (at least regarding oxygen). The cans are irrelevant. Legally, you didn't need any O2 at all. They're seeing how both they and their aircraft perform at high altitudes in preparation for a trip where they're going to need to be at high altitudes. They're preparing and they're learning. If only all pilots would do such things, we would have much fewer accidents. And by posting about it here, we can offer suggestions based on our experiences that will make their next flight safer and easier. This is the highest calling of hangar talk. If you feel the need to poo-poo it, why don't you just take your ball and go home?