LEDs are solid-state devices, CFLs are gas-filled tubes...
LEDs should have an extremely long life, and provide even light output during that lifetime. They are similar to transistors, however, and there is always the sight possibility of a single LED component itself failing. It should be extremely rare, however, as LEDs require very low voltage and current.
CFLs require high voltage and current to excite the gases - usually the inverter board driving the tube fails before the tube itself - and if it fails slowly, the CFL's light quality will suffer before complete failure.
The LCD itself may slowly fail in tiny spots of stuck or dark pixels over time, as the gate diodes degrade, but the most common reason for extensive LCD failure is physical damage. The LED backlight will probably outlast the LCD gates!