I think Teamwork is a great and essential tool in ArchiCAD and any CAD software for that matter. But there is a definite problem with the amount of time it takes to sign-in, sing-out, send, receive changes, etc. I am guessing that each time changes are sent the whole file needs to be modified and recopied to its location, or something along those lines?? There must be a way some 'tricky' programming can reduce the time spent doing this procedure?
In case you were about to suggest a work-around by limiting the time spent sending and receiving form the files and using drafts but this does not fix the problem.