If you don't overclock, it only takes a halfway decent motherboard to live a very long life. An EL-Cheapo will stress it's parts much more and won't last more than a few years. On the other hand, a quality Mobo can take a pretty harsh beating and still come out on top.
As you overclock, all involved components are forced to work harder. As you approch the absolute maximum ratings, it has an negitive effect on the life of the motherboard. The closer you get to Max ratings, the shorter your mobo will live. Each part has a maximum voltage, current, and temperature rating. Quality mobos will be far from them, where an el cheapo will save production costs by using cheaper parts. If you making a million, each penny adds up to $10,000. That is 10 pony rides per day for over 27 years at my local Meijer.
10% overclock means a completely different thing to the cheapest mobo that can be overclocked and the highest quality. It's going to shorten either one's life. The difference is going from lasting 8 years to 5 years or 20 years to 18 years. I pulled those numbers out of the air but I think it gets to the point.