Why do pilots' masks have more oxygen? When a commercial passenger airliner suffers a rapid decompression, it is critical that everybody on board gets oxygen quickly. In the passenger rows, oxygen masks connected to chemical oxygen masks will drop. In the cabin, the flight crew will pull out their oxygen masks, which are connected to pressurized oxygen canisters. The chemical generators will last for 10-15 minutes, but apparently the flight crew's oxygen supply will last for a couple of hours.

Why would the flight crew's supply last for so much longer? If the plane isn't at a breathable altitude after 30 minutes, it seems like it'd probably be unrecoverable, and the passengers will be in irreversible comas anyway.
The pilots also need to use oxygen in case of smoke, fumes, or fire in the aircraft.  Thus, they need enough oxygen to be able to get down and land in a fire scenario, which is much more than a decompression!

Fire procedures have the crew on 100% oxygen at positive pressure to prevent them from breathing in smoke and fumes, while in a decompression, their masks mix oxygen with cabin air, in much the same way the cabin masks do.  This is also why the cabin masks are not used in smoke/fumes scenarios.