Seems very reasonable to me (notably for niche DIY electronics). Have been in Hypex place and forecasting is tricky enough usually. End of life forecasting is a whole other level of uncertainty and parts are even worse. Often end up with too many and have to write them off. After a few years, many hobbyists are likely itching for an upgrade too. Am guessing Hypex ability to repair would likely be even longer than 5 years.
May be that I have lower expectations, but how long do you think Hypex should support?
Well, I own an hypex based amp (commercial one, not diy) since aprox one year ago. Before that I had a Yamaha that I used for like 10 years and sold still working and before that I had a Sony that I believe was close to 18 years in use. So yes, I hope my hypex can be repaired for well beyond 5 years from now, as I believe many owners, certainly not all, but for sure many, hope too.
What is inside the box, if it is niche or is easy or not for the company to keep stock, is not my problem and I could not care less nor I am going to research when I purchase something.
It is true that maybe, only maybe, diy stuff goes by different rules and expectations, but still cost good money are are certainly not mean to be consumables. Just my opinion.