There's a video on Youtube of a Focus that has an overheating transmission. The computer basically asks you to stop the car and wait XX minutes before resuming.
I seem to remember someone on this forum posting a story of the car basically shutting itself down when the transmission overheated. That, to me would be the same as being stranded.
In regard to longevity, I don't know how a transmission that makes such horrible grinding noises could last very long. Mine isn't doing it (yet)...I'm referring to some of the videos that people have posted. I'm imagining a lot of metal shavings sitting in the bottom of some of those gearboxes, and once the gear teeth wear down to a certain point and begin slipping past one-another, game over. I think we'll be seeing some failures on this forum or on YouTube when the miles start racking up on the cars that are making noise.