I think tires will easily last 40 mins, I'm still going faster on them after sessions of up to about 30 mins.
If you're blistering them it normally means you're over-working them or have done 1 skid more than you should (i.e. you've a big skid, spun, or had too little ABS interference
).
The Porsche cup is quite a nice car to drive I think, as you'd expect given it's pretty much the same car as the GT3 Cup car from AC that we all like.
Haven't tried the Lambo ST yet, although it looks cool so i need to.
I actually quite like the NSX, but haven't written down my lap times in it so no idea how fast it isn't versus the rest (has ACC seriously got no fastest lap screen? Or am I just utterly blind?).
I could be tempted to run the series, but it'll be pretty limited I would have thought given the tiny number of car and track options.
I have some ideas for things to maybe spice it up (using the 911 and ST as Jokers for instance, with a points multiplier but free choice which race they have to be used in for example. If they're far enough off the pace and the interest exists for longer races (these cars should really be circulating for an hour minimum I'd argue, that will naturally bring in pit strategy and allow for random weather to do it's thing) then they become a legitimate slower class of backmarkers to introduce a new element to the races.
Only issue is that if you are the only driver to play a joker you may be quite lonely - option 2 is you MUST play your joker at one of 3/4 specified rounds as this should ensure a few fellow idiots. I dislike forcing a hand like that though as the whole point is it's down to the driver to weigh stuff up and make the leap of faith..
To start though, something along the lines of Jeffreys' test plan with no silly added rules would be perfect to help ease people in and also makes it clear in advance what sort of weather to expect.