How long is coffee with creamer added safe in a thermos?
The clock on the danger zone starts when the food temperature drops below 60 celsius. It should be 4 hours for coffee - two hours are for meat, where it is assumed that bacteria in it have had some chance to grow while it was being butchered, transported, and stored in a supermarket. In coffee and creamer, there will be no bacteria growth at all in the ingredients, it will start after you have brewed the drink and mixed in the creamer, and the temperature has fallen below 60. 

If you want to go by the book, measure the temperature of the coffee inside the thermos 5 hours after brewing. If it is above 60 Celsius, then it is still safe up to 9 hours after brewing. Do it on several days to have a significant result.

(For those of us on my side of the pond, that's 140 degrees Fahrenheit. )