ytrewq wrote:

" In the absence of the shuttle, visits to the station require two Soyuz
vehicles: one docked as an emergency escape pod and one to transport
astronauts to and from the station, an arrangement that NASA would not be
allowed to benefit from after April 2006.

This isn't right.

Usually there is only ONE Soyuz at the station - the one the last crew used to fly to the ISS also serves as the escape pod.  The vehicles are certified to be reliable for only 6 months - the normal duration for a crew stay on the ISS.

There are 2 vehicles docked to the ISS when the crews are swapped - the old crew returns to Earth using the old Soyuz while the new vehicle stays behind.