its a bit more complicated than that.
1) apache will timeout after a bit
2) the web browser will timeout on an upload (good luck changing this with IE)
3) php.ini has its own timeout/max file size
4) the file input type has its max file size
then add in the airspeed velocity of an unladen swallow. (European or African?)
my suggestion is to use java (messy) or have the user upload via ftp (but most users can't figure out most ftp clients)