"servers have a useful life of five years"
That is interesting. I know nothing about server loads in the Cloud, but I'm guessing that they're more hammered than many on-premise company servers. Does that have a real impact on hardware life ?
I mean, sure, the disks will need replacing every now and then, but that depends on the disk, not on an arbitrarily-determined lifespan record. I've just bought a few 8TB NAS discs for my Synology. They are guaranteed for the EU-standard 2 years. They will likely have a much longer useful life, but they're spinning rust. I will use them until they fail, not until the warranty runs out.
So five years for a server, why ? CPU and architecture progress has slowed to a crawl, and I seriously doubt the newest USB protocol is a requirement for a server.
So, if you replace the disks when they fail, why throw out a motherboard if it's still working ? It's not like a CPU slows down over time, its cycles don't wear out like batteries.
So why set an arbitrary limit of five years for kit that could well do double that ?