Bug/Issue Mac OSX slow down after a while (throttling?)

Hello,

I have a 2.7ghz i7 macbook pro with 16gb of ram and a GT650M chip (1GB onboard memory). It is running OSX 10.11.6
The game runs very smoothly at first however after 60-90 minutes the game slows down. I start getting mouse lag and frame skips... The computer gets warm but not THAT warm, this rig should be able to keep up with Starbound (omg why would you buy a mac for gaming noob ... there I said it before you did)

Sure I could lower the settings to a point where this wouldn't happen. But in the first 60-90 minutes it runs like butter and I don't want to reduce resolution when I know it's capable of sustaining it ... for some time!

Has anyone run into this issue? A quick google search reveals Mac's do tend to throttle when they get hot or start to max out the power supply (85W)... Is that what I could be running into?

Even better, has anyone fixed this via some system settings? I am already running a fan control software to max out the fans when I run the game. It seems this has delayed the problem somewhat but it still appears. Next step is to open the back cover and clean out the dust which may be accumulating there...

Thanks guys!