[peeters]

Also I believe the seats are all custom shaped for each astronaut's body. I'm sure in dire circumstances they could use a capsule that wasn't designed for them, but it's very much a case of each astronaut having a very specific seat designated for the ride home, rather than "do we have enough seats".

[jccooper]

The seats can be removed and swapped. They can, and have, gone back on different vehicles than they went up on.

[sandworm101]

The custom seats mean you cannot use someone else's. You wouldnt fit (if too big) and would obstruct things. I may be possible, but would never be part of any plan. There are also weight/balance issues to consider.

[stjohnswarts]

so you better not have that last gallon of ben and jerry's before you take off for your 6 month space station stint.