Joe,
Your experience with Heritage is what I was talking about in terms of lots getting to retail quicker than the all-night bidding, the vast majority of those that never got another hit after the 11:00 hour were probably already full priced or the next increment would have placed them over market.
On the one lot that I won in Heritage(two auctions ago), Myself and another bidder began battling at the start of the extended bidding when I came in to place what I would hope would be the winning bid at 10:59 and played ping-pong for nearly an hour, more than doubling the price of the item from when we started, I am sure you can guess what it was
If that would have been a 4-5am auction, I would not have bid until I got the final notice or warning and chances are he was not around to bid as there would not have been one bid since he was the high bid before the extended bidding, thus no reason for him to even think he might get outbid. The premise of an auction and especially a successful one for the consignor is to create a bidding war and that can only be done when all of the qualified and interested bidders are front and center and battling it out. Thus a higher sales price, the more bids the higher the price.
As others have said, there is no 100% answer and you just have to plan each auction around the bidding parameters.