I expect to get the rest of this decade out of my Steam Deck so IDK, very different to my normal expectations for a computer. The Steam Deck also defines a floor that will allow compatible games to be very performant on the Steam Machine so I think that will help the Steam Machine have a decent lifespan.
I also think on some level we need to start resigning ourselves to getting 10+ years out of our computers!
I'm hopeful that with the insane hardware prices right now, studios will be forced to actually make their games work on older hardware.
Until they want to play Fortnite/Roblox/whatever else.
a) they already use Linux, but want to buy this anyway just to encourage the ecosystem
b) they want to recommend it for the normies they know, who find Linux, or gaming on Linux, daunting
So my point still stands.