I think these lifetime claims and the warranty, for that matter, are there for one and one reason only; they want you to choose to buy the bulb when you are looking at it. Marketing and NOTHING else.
First, if there is no warranty, they can pretty much say whatever they want. What are you going to do if your 25,000 hour bulb dies in 24,000 hours, OR 5000, or 1000?
Second, lets say they do have a warranty like some recent Cree bulbs I bought. One died in a few days, the other a few weeks. If they are very recently purchased, you can return them to where you got them, but then its really just Home depot or Walmart taking the lose. So back to Cree and the "warranty." I didn't keep the packing of warranty text for the Cree bulb that died, so i went back to the store to read the warranty. To get a new bulb just send the bulb to them with ME paying the postage, and include my cash register receipt. So I need to spend $6 to send them back their defective $8 bulb, assuming I have a copy of the cash register receipt. Then wait 6 to 8 weeks or more for my new bulb. Anyone see a problem with that?