Yeah, I did it at KBF as well. With MZR, they let us stay on the ride 3 times in a row.
With SFMM, it really depends on the ride, and the operators. I once went on scream 8 times in a row. A few hours later, we tried to do that again, and they wouldn't let us.
Disneyland RARELY lets you do it. But, I did it once on Splash Mountain.
I am DYING to try to stay on Haunted Mansion. See what's behind that exit area. Even if it's just wall, I'd still be interested in seeing it.