Chain down, chain down - chain snap, snapped chain, chain break, broken chains

My SRAM chain snapped when I was pulling away at a traffic light. It looks like one of the links has just been pulled until it snapped. It had been cleaned in the last month or so, and is only about 7/8 months old. I had heard a creak every now and then when out of the saddle going uphill etc. I can't think what could have caused it to snap as I checked for stiff links, and it was not under too high tension. The only things that come to mind are;
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Once a week would be a better option; keeps it running better and you notice problems sooner.