Fully buffered workstation memory is not like normal RAM, the error correction makes it work very hard and heat up significantly. My RAM regularly hits 70-80ºc during heavy use, even with the heat sinks attached this is strenuous for such components especially long term.
This is why you should only buy RAM with a lifetime warranty, you never know what could happen further down the line.
My Mac Pro has run 16 hours a day every day for 4 years, 2 sticks failing during this time is unlucky but not really unexpected considering such a high level of use. Memory America stand by every stick they sell and replace the whole shipment to ensure you retain matched pairs and avoid a repeat failure should that batch happen to have a manufacturing flaw.
If it all gets made in the same place then you should buy it from the company with the best pricing a
nd returns policy. That would be MemAmericay then...