Back in the (late) 90s, for $10 or so, Elwood would record a customized "you've got mail!" message for you. I had him create one for my (now) wife, using her real first name, as well as her nickname. "Elizabeth, you've got mail!"
Never. Never is the correct answer. He's been delusional his whole life.
Heat.
While the actual LEDs (*) may be rated up to 20,000 hours+ in optimum circumstances, but the actual 3rd party bulb manufacturers, especially the cheapo brands, are building bulbs with poor heat dissipation designs and cheap and/or poorly designed circuits. Same goes for other parts they may use, such as the power supply. To reach 20,000+ hours, you need everything - not just the LED - to be working optimally together.
(*) the best LED makers out there right now, e.g. Nichia, Cree, Phillips - really do some amazing engineering.