I should add if we've only got 3 hours at the venue, and more than 10 of us arrive, there'll only be half of us racing at once, so there won't be time for 2x 1 hour races each. TBH I think 45 mins would be enough and that might still be a little too tight for time, depending on what else they've got booked that day.
Regarding practise, I did practise a little beforehand last time, and even by the end of the session on the day, I was still 2 seconds a lap slower than what I could do at home (and with the same set, no less!). As soon as I got home, times were back what they should be have been. I just suck driving with worn out Momos, especially when the FFB was set up all wrong (100% spring and damper force with LFS = bad, mmmkay).
Edit: Chris, yeah, it was nearly 2 years ago, and I can't see how they have the space to double the number of booths. In fact having a break while watching the others race is (or was) part of their selling talk.