Only logic I can think of here is for people to buy one to have on hand if/when their glow plug goes bad to use while they wait for the replacement to be shipped out. Can’t see how they wouldn’t cover it if it went bad.
A "trick" used in the automotive world is "consumable parts," like brake pads. Light bulbs or assemblies fit in that description as well. If the glow plug only has a certain number of cycles in it's life time, I'd suspect that glow plugs are not covered under warranty.
They have been replacing them for free and I wouldn't see that changing for the time being. But. Truth be told, they are only rated for a 150 starts and are a wear item.
I didn‘t realize the glow plugs were only rated for 150 starts, how is this an improvement over the hot rods others use? Camp Chef and Traeger hot rods are like $15-30 and last for years usually. Others have gone to lifetime guaranteed ignitors.
They have been replacing them for free and I wouldn't see that changing for the time being. But. Truth be told, they are only rated for a 150 starts and are a wear item.
That's the critical bit of knowledge to have. Early failures should be replaced under the device warranty, but with an expected 150 starts, I wouldn't be surprised to hear that after about 100 starts (arbitrary number on my part,) that warranty coverage on the plug will get denied.
I contacted support a week or so ago and yesterday I got two of them delivered. Give them a sad story and I think they'll come through with a free one to have for when it does go out, and it certainly will if you use the pit a lot. Make sure that your pit is registered with them.