Aussie.
Mate has many meanings.

In my experience, fans don't really fail. Their bearings get noisy, but they keep spinning.
I'm sure many have, but the odds are you'll know about it long before.

Of course I'm not expecting a 30k fan to die immediately after 30k hours.

However, if a manufacturer is willing to declare 70k hours on their product vs 30k of another manufacturer, that should say a bit about the materials being used.

Same for the PSUs: Seasonic and FSP are declaring 100k hours, other brands I found online were only mentioning 40K hours. That means - just speculating - that 85C capacitors were being used etc. Of course it doesn't mean that the 40K PSU is going to suddenly die after 40K hours.