Sounds like a reference cooled 760 to me, install Afterburner and set up a custom fan curve so that the fan kicks in at a certain temperature level.
79 degrees under gaming load is a reasonable temperature, the 760 normally should be around 81 degrees under load. You should only start worrying once temperatures reach 85 degrees or so.
Blow out the fan on the cooler with a can of compressed air every few months and it should be fine.
For the moment, as long as games aren't crashing on you etc. I wouldn't worry too much.
For reference, my GTX 260 runs at 80+ degrees and it has lasted me 4+ years