I understand where the skeptics are coming from, and don’t fault them a bit for waiting until we’ve shipped to decide. Early adopters like us get the fun stuff first, but as the proud backer of 115 Kickstarters (!) I can attest that we early adopters have also been known to receive the short end of the stick from time to time. This won’t be one of those times, but they don’t know that. Glowforge is going to get you all something wonderful. We’ll get them something wonderful too, later, if they want it… they just will have to do without for a while. 
I also don’t fault them for asking us to “show our work” and reveal our sources, designs, and so on. If I was skeptical of someone but really wanted to believe, I’d ask too. For practical competitive reasons, we won’t answer those questions, but it doesn’t hurt to ask.
There are a few questions in here that I can answer though, which I’ll do my best to do here:
- The Basic model is water-cooled and has radiators that shed excess heat. The Pro model uses that, plus a second thermoelectric cooler and radiator.
- There’s no agreed upon standard for expressing filter life - at least, we haven’t found any of the other laser filter manufacturers’ answers to this question. (If they have, please do point me to where so we can compare!). We’ve said that we expect to have replacement cartridges available for <$250.
- We will sell and ship tubes guaranteed against DOA. They are user replaceable.
- The lens is protected by purge air, easy to clean, and easy to replace. When you get yours you’ll be pleasantly surprised by just how easy, in fact, it’s a pretty cool mechanism.
- Ditto the two windows that protect the mirrors, the output coupler, and the back side of the lens.
–dan