I am all for longer races. I love 12th scale 8 minutes. That rocks! Longer races take more luck out of the racing.
The extreme opposite would be a 4 minute oval, for example. If you get hit by someone and lose a lap or two waiting for a corner marshall, more often than not, there's no hope to regain the victory. However, with a long road course race, you have more opportunity for the better drivers to recover from something unlucky.
In my experience, there is usually PLENTY of time that race tracks can make up in between the races. Most of this wasted time is poor efficiency of the person running the computer. Breaks in between the heats or mains can be reduced or eliminated altogether, and this will not have any effect at all on the time you have to work on your car or charge batteries.
I think we all agree that we enjoy not having battery wars. That has been a very enjoyable change to the hobby over the years. So as long as this doesn't come in to play again, I'm all for extending the time for all classes. I know that I've never had problems with battery run time with 12th scale at 8 minutes. I'm sure that Touring cars could handle more time too.
With the brushless motors coming on the scene, battery run time becomes even less of an issue since brushless motors are more efficient than brushed.