Depends completely on which Mac you have and also where you play. In normal questing PVE it should be more like 2-3 hours is normal currently with default settings. Longer if you reduce Texture Quality down (depending on your graphics card and spec) Last night I played general questing 3-4 hours at Ultra-High with Shadow Quality set to Medium before relaunching game when the memory go close to limit.Frame rate and gameplay works just fine but random client crashes every ~25 minutes means you pretty much have to play with medium or low settings.
Why is it weird?Wow. So, Moonie, you are claiming that the crash rate is related to the resolution and the graphics settings.... that is... umm.... weird.