At 2am there probably won't be a lot of auctions ending, so a shorter lead time would probably be safe. I say probably, because nothing is guaranteed with e-Bay. E-Bay has also been known to go down during the early morning hours for maintenance.
If you put in a snipe of $11.00 on an item that's sitting at $10.00, the $11.00 bid could win provided that someone else doesn't outbid you. If it's sitting at $10.00 you have no way of knowing what the proxy bidder's max is. Chances are good it's higher than the $10.00 shown on the screen. If the proxy bidder's max IS $10.00 another sniper could still come along and also bid the same amount as you (or more), and if both your bids are equal and his/her bid gets there first, that's the bid that e-Bay will honor. When sniping, always bid the max you are willing to pay. E-Bay will only charge you one increment above the next highest bid if you win. In other words, you won't end up paying your max unless that's what it takes to win.