If you overheat tire surface once, you can expect it to get back to normal quickly. If you keep overheating tire surface often, you can expect temperatures inside tire to get higher as well and tire surface will not cool down so easily.
Thanks for the reply K Szczech, just so I don't get dog piled by the forum I want to state that this is only my assumption here. I'm no pro racer even if rF2 makes me feel like one and, sorry, doing my best to keep the response short.
The first thing I thought was perhaps I'm driving the car too aggressively and I need to dial it down some. I can work around it as you suggest but my point is that we probably shouldn't have to be this careful in a GT class racecar. Downforce plays a large role in the tire management for open wheelers and since GTs don't generate that level of downforce the tires shouldn't go off as quick. The type of tire is also very important.
e.g. I watch a lot of motorsports over the years and open wheelers have to manage their tires carefully. Just the past Indy race at Barber that was said to the race leader. Schumy complained a fair amount last year in F1 about the Pirelli tires and how drivers couldn't push hard with them thus affecting the faster guys. Part of this is done on purpose by Pirelli to add some dynamic content to the races.
In GT racing, this is still a concern obviously, but those guys drive the absolute crud out of their cars and sometimes double stint their tires. The Corvette race team does this a fair amount. In-car race cams shows those guys just hammering those cars lap after lap. The last FIA GT race in France a week ago, the drivers attacked non stop for 30 minutes before they had to pit.
I can duplicate this in rF2 but for only a short time. Again, lots of different variables but doing high 50s avg at LimeRock with uphill chicane, that is moving well but I should be able to keep that pace for longer than 7 laps. I would think I could do this for a good 20 laps or more. The C6R should have durable and grippy Michelin's but it feels like (just my opinion) I have some very F1 modeled moody Pirelli's.