Hey there brndwn, your temps with furmark are absolutley normal, although a little bit on the hot side.. 80-85 is the normal range on G75s OC'd to the maxx stable settings running furmark.. I get the same figures lol..
But yea in game you will never hit such temps.. at 750/1700 i am usually around 74 stable, but C3 beta, planetside 2 and guildwars seem to get it extra hot but still my stable temps are 75 usually, but you room ambient temps also makes quite a diff.. with my windows closed and heaters on ive hit 78 sometimes playing GW2..
I would say try and keep temps at 74-76 max if you are gaming for long periods at a time to preserve the heatsinks and have it last longer..
🙂