I'd imagine it completely depends how you are going to drive the 'Ring.
My view is that 7 or 8 tenths is probably where you need to be at on an open day with all sorts of cars and traffic. So much to go wrong very quickly on the Ring and might not even be your fault.
In which case, the GTI is not a heavy car so the brakes should be fine.
Back to back laps might start to affect things though. We did in 3 laps back to back (with a driver swap after each lap) in a 1 year old Cayman S some years ago on a very warm, German bank holiday in May. The clutch went to the floor on lap 3 so we stopped for a break after that and managed a 4th lap and it was fine.