First and foremost, "futureproof" is something we only chase in our dreams.
The choice of motherboard or choice of components imho, especially pricewise, might not have much to do with the period of usage/ownership of a computer.
It is usually dependent on one's budget and requirements from that computer.
We may spend more on something important and save a bit on something not that important for us.
eg. sometimes someone may say pc mainly for music and we may suggest as powerful processor as possible, etc and there maybe hardly anything left even for a good set of speakers.
Maybe we should start off with a good/decent set of speakers and a good sound card(if reqd by buyer) and then fit in a well-balanced config in the amount left.
I personally have always valued motherboards very highly- after all it is called "mother"board for a reason- as it sort of nurtures almost all other important components.
The full potential/functionality of other components is critically dependent on the motherboard imho.
Overclocking or not, a better (and usually pricier) motherboard does offer more value in terms of better design, better build/component quality, greater reliability/stability apart from the extra features/benefits.
This depends on individual perception and is highly subjective.
eg.
One person is happy travelling in a WagonR while another does the same route in his Civic.
Fact is, both may crawl in the same traffic/pothole-infested road at not much more than 20Kmph most of the time.
Will the Civic user want to be in a WagonR or any other small car that may be much more cheaper/fuel efficient?
Sometimes, we do tend to term something as overpriced/unnecessary just cause there may be something cheaper available.
p.s. examples may not be very apt but couldn't think of better ones for now- sorry.