There is a saying about thrust and bricks around here somewhere... one example does not the ecosystem make. That said there are examples of SoC's which get attention and manufactures which do a better job than 3 years, but its the exception rather than the rule, and the updates frequently are quite late.

If your willing to dedicate an engineer or two to keeping it running then so be it. I can assure you that your average 10 year old PC running Linux probably hasn't gotten that much attention since before it was released. But then again, PC's adhear to industry standards and are mostly iterative designs.