I've got 50 HPDE days on my car and I periodically send a sample in to Blackstone with the last one done in February of this year. According to Blackstone the tests have not revealed any issues. I change my oil every 6 track days. The biggest impact seems to be the heat shearing the viscosity enhancers in the oil causing the high temp viscosity to drop from the original 40W to a value of bit over 30W by the time I change the oil.
edit: To the OP, looks like fun. That C7 was definitely in over their head, especially if that was an instructor group. I wonder if the Peachtree chapter is like my local chapter where they mix together the advanced, intermediate, and instructors into one run group? I avoid doing events with the local BMW chapter because traffic in that group is a hot mess.