Actually, I would expect them to support every hardware generation in terms of replacement parts effectively indefinitely.
Since GF have chosen to market a product which will deteriorate with use, they have to support their customers by providing replacements for hardware until the last customer using that machine moves on, or provide a suitable upgrade path which makes that spare unnecessary.
I believe GF already has every intention of supporting us long term based on their conduct so far, but hypothetically if they were to tell me in a few years time that they no longer stocked replacements for their custom made Gen 1 mirror I would be extremely pissed off.
I’m not sure which machines you are referring to when you say “finding things for machines even one gen old can be a hassle”. I manufacture, support and repair industrial machines for a living, and the idea of a company that markets a machine and then declines to provide ongoing spare parts for it is completely alien to me. No company I have ever worked for or interacted with operates like that (even the companies that I don’t consider to be customer focused)
Edit to clarify: I’m only referring to custom made parts that we can’t get off the shelf elsewhere. GF only needs to ensure spares are available somewhere