FYI to anyone reading this you cannot resubmit if your tutor downloads your assignment, meaning you can submit at 11:59AM version 1 of your essay and then resubmit revised version 2 at 2PM and if your tutor logged on at 1PM to download the groups essays (this happened to me) then your resubmitted work during the grace period will not be marked. If you submit after the tutor downloads then it seems you merely go to the back of the pile for marking.
Finally if you actually read the boxes you tick for agreement upon uploading your essay you will find that you are agreeing to allow your tutor to mark this essay if they download it early, so I think this even applies days before the deadline. I would advise to only submit versions you would be happy to have marked and only use the re-submission as a tool to correct errors you later realize..
I personally would advise against resubmitting work, its best to just submit it when your ready of course dont make it 11:50PM and your internet go down LOL.