Personally I have had up to 3 boxes connected to CREATE at the same time.
However you face other issues in the upload of code as USB connection based boards will presently only upload from the computer it is connected to.
Some boards namely the YUN can however be programmed from many PC's using its IP's so long as they are available on the subnet.
Having done this I can confirm it works great.
Other than that you might need to allocate somebody to do the actual upload after a code change but dont forget they may need to refresh the CREATE page to see those changes.