Well, friction is a b----. That's why its hard to have extremely long coasters without multiple lift hills or launches. Multiple lift hills kind of defeats the purpose of a "long coaster" and takes a lot of people out of the experience. It can work if there's a theming purpose for it (like mine trains) but from a design stand-point its usually avoided. We've seen more multi-launch approaches now with Maverick and Full Throttle, but as they're launched coasters, the ride time is still pretty short.Still, the average in the non-Disney amusement parks is longer coaster rides (2 - 3 minutes), while Disney seems to think riders will be content with a 1 minute ride wedged into 15-30 minutes of pre- and post-shows... With all the money they have, I'd like to see Disney approach a 5-minute launch-to-brake coaster experience!
I think that you'll find that if you had 10 minute long coasters, people would get bored and wonder what's the point? They would get bored with being dragged along at 4 MPG by flywheels and with the excessive lift hills. And going back to my first point, friction hits you a lot harder than you would think. Its tough to complete over 5,000 feet without a 75 MPH+ top speed without grinding to a halt in the end. And if you want a mid-course block for 3+ train ops, its going to make the train even slower coming into the final brake run.