Where did all these G70 3.6 come from?! Is that a secret order code most of us don't know about?
Joking aside... I did an HPDE Track Day at MSR Cresson on the 3.1-mile CCW course back in Oct. 4 20-min sessions, so I'm pretty sure I did at least 20 laps and no less than the miles you ran. All except the first 10min or so were hot, though it was my first track day in the
Stinger, so the morning 2 sessions were learning the long 16-turn course - and the car - and consequently not all out balls-to-the-wall.
I started with brand new EBC Bluestuff brake pads that have had less than 600 miles of very easy break-in miles, 1/2 of which were pure hwy cruising. First 100-200 miles was seating the pads to the rotors, followed by the 1st stage bedding in, per mfr's instructions. I then finished the bedding process at the track, as the required temp can realistically only be safety achieved there.
This pic was taken at the end of the Track Day. The end bevels were pretty much gone, but plenty of meat left on the friction material. I could easily do another similar track day, though attempting a 3rd one would likely not be a good idea. Once the pad is worn down to the last 1/3 or so, wear will be accelerated, as much as the twice the rate as at near-full-pad-thickness.
My guess is that you either started with worn pads (seems unlikely with only 8000 prior miles, though not entirely impossible), or you were cooking the pads to the point of rapidly accelerated wear. To know for sure, you would need to know the conditions of your brake pads prior to the Track Day. It's always a good idea to check before any lengthy event. For us, we swap to our track
wheel/tire set upon arrival at the event, so brake check is conveniently done at that point.
At any rate (pun intended), brake pads and rotors are consumables, just like tires. Picking the right components for the job helps, but high performance driving will invariably lead to higher brake wear rate. Period. That's just the nature of the beast. Brake systems do their job by converting mechanical energy to heat energy - generated by frictional materials. You
will wear down your pads or your rotors, typically both. Longer lasting harder pad compounds will chew up your rotors at the track, but that might not be as noticeable. Most folks don't mic their rotors' thickness before and after event (I do

), but brake pad wear is much easier to recognize.
I look at it as part of the cost of having fun. Just a rough estimate... my brake wear for that one Track Day is probably around 1/3 of the registration fee. Even less when all the expenses for the weekend trip were added together. Not trivial, but all part of the cost of tracking a car.
The G70 is not a sports car. The
Stinger even less so. You can call them sport sedans or whatever you like. To me, they are GT cars - Grand Tourismo. Better handling and more power than the typical everyday sedans, but kinda heavy and not as sharp-edged and tunable as dedicated track weapons.