Hi folks, my tuppence worth...
When setting last week's peer review I found the flexibility of being allowed to amend the closing time 'due to unforeseen circumstances' very necessary. Closing time was set at 6.30pm previously but I had to be gone by 5 that day. I appreciate that the setter is less involved than the setter/judge in clueless but it's nice to be there at the end to sum things up and post the prize.
I think that as long as it's clearly stated in the opening post and is somewhere near the regular time the closing time should be reasonably flexible.
I also say multiple entries are great, one vote per entrant and if someone doesn't vote then we should all appreciate that an afternoon nap is often far more important ;)