You need to maintain both the software and hardware. It is not just that time an installation may last but the time the ecosystem stays viable.

There are many CPU architectures, even some that became quite popular, that have gone extinct. Some lasted less than 30 years in total.

x86 has lasted decades but, as it relies on only one to two companies, it is not guaranteed to do so.

But the biggest risk going forward is geopolitical. You may completely lose access to a technology even if it continues to be available elsewhere. If you are in Europe, technology from the US in particular may be a concern. I think that is the main motivation for this project.