I've bought motherboards over the years made by MSI, IWILL, ASUS, PC CHIPS, and others I've probably forgotten and while I have had boards fail before I've never had a manufacturer not stand behind their product and offer a replacement for an unusable motherboard before this.
These replacements you got, were they for boards that were out of warranty like your DFI? If so, please tell me your secret.
I'll not go into the details here but I've had board replaced as cheaply as free shipping both ways or as cheap as return shipping cost only, even when no longer under warranty. Not every motherboard issue is expensive to repair and a company may be willing to do so at or near cost to satisfy a customer.
My experience with DFI was less than helpful and amounted to them quickly offering me the chance to spend $40+ to get a board refurbished that isn't worth any more than $50. At that point I'm better off putting that money into a new motherboard. If they had offered to repair it at a more reasonable cost I wouldn't have blinked at paying for the repair. More importantly if they would have addressed the issue on newer designs or offered me a chance to upgrade to a less troublesome design at a reasonable cost I would have given them the benefit of the doubt as a company that may be trying to improve product quality.
As it is, I see the fan design on these boards as limiting the useful life of a product unnecessarily. I have studied the chipset fans on every motherboard I've come into contact with since and I've realized this fan/heatsink setup is below average quality for the PC motherboards I come into contact with on a regular basis.
If DFI paid a few cents more for a thicker heatsink on the chipset and a few cents more on a better fan I'd still have a working motherboard instead of a paperweight that would cost more than $40 for me to get refurbished.
Thus to me, they have designed themselves into a reputation for poor quality on the low end boards that have this specific chipset fan/heatsink.
Maybe you think that I shouldn't share the lesson that I learned. But maybe it'll save someone else $40 down the road and they'll be glad I didn't keep this experience to myself.