I did have an awesome instructor, after the second session (first session was under heavy rain) he said i should go to intermediate but our group was only 5 people, so it was like a private track. makes it much easier to learn. (i usually screw up my line while following someone very close).
I didnt find lightning as a very exciting track - it might be because i didnt have anyone in the group to play cat and mouse with. I had that in VIR, definately caused me to push harder.
I had gassed out brake pads that felt like wood, with stock brake fluid that probably boiled. Pure stock car with PS2s. On the straigt areas especially the main straight i wasnt pushing hard and (on main straight) literally taking my feet of the gas. My lap times were only 3 secs lower than a intermediate M3 with track tires and BBK and dinan stuff. surely there is always room to improve, but lightning, two days in a row? I would say one day is enough.
BMW M3 E92 - Silverstone II