I have had 10 ASUS P5E-VM-DO motherboards in service as file servers /with 8GB of RAM and Adaptec 3805 RAID quite literally since the veryfirst of these boards hit the distribution channel in Canada. That's what, 5 years now? 6? My home lab is largely composed of vPro ASUS motherboards and a significant chunk of my primary lab as well. (See here: http://www.theregister.co.uk/2012/12/31/building_it_test_lab/).
In my experience higher end (read vPro or equivalent) profession/workstation-class desktop motherboards fail less than server boards. This is because they are significantly less complex than server boards but manufactured with the same high-quality components.
Lower quality motherboards (Asrock, ECS, bottom-dollar ASUS/Gigabyte/MSI boards) are the worst of the lot. They are still made with liquid caps, have dirty volt regs and the traces are made out of what seems to be easily evaporated pot metal.
I trust a quality manufactured Micro-ITX motherboard designed for a home NAS far more than I do an EATX monstrosity powering a 4U HP superserver. The Micro-ITX is probably made from the same top-bin parts, but is so much less complex that the failure rates are way, way lower. Give me 2x quality desktop boards in the same chassis with literally every conceivable component duplicated, wrapped into a cluster. I will take that before your "statistically unlikely to die, 4 hour service life" enterprise-class server.
My design costs the same (or less) but offers complete redundancy and is statistically less likely to have even one of it's nodes die than the Enterprise version. If I can't shoot one of the nodes and have the overall system still working, then it just isn't good enough.