This is something that I've discussed with a couple local racers.
The discussion came about because we already run 5 min qualifiers and a 10 minute main for our TCS Mini class. Now, with the higher capacity of the Lipo batteries and the lower power consumption of the BL motors, we are starting to notice that we are only using slightly more power per race with our TC than we are with the mini. (mini~989mah, TC~1128mah/per qualifier, depending on track layout)
So when the power consumption is so low, you start to feel like your leaving a lot of time out on the track. And I often come off the track during qualifying and in the TC class main feeling like "was that it...its over already".
I don't think every class has to go to 10 minute A-mains, especially if your at a facility that has huge turn outs every race day. But somewhere in the middle would be nice.
Something like:
TC...6 minute qualifiers + 7~8 minute mains(or A main only if the crowd is too big)
TCS mini...6 minute qualifiers + 10 minute mains
1/12...its been a while since I watched one, but I think their races are already pretty long aren't they?
Anyway...thats my thoughts.