There are a lot of variables that can affect the lifespan of a motherboard, and I've seen motherboards that break from first day of use all to way up to a couple decades. However I can vouch that a decent quality mobo shouldn't last only 2 years (I do expect it from Dell and other OEM mobos though). There may have been issues with it in the past that have gone increasingly worse until now they are manifesting in a way that cannot be ignored.
Hopefully this resolves everything. If you find that this does indeed fix things, then make sure to come back and mark this thread as solved so that other web denizens with similar issues can venture here and take notice. Thanks!