My thoughts have come to be that the ball's in your court until you throw that bid down. You see an item and come up with your max number. I've noticed that a lot of shill accounts are newly-minted with little to no feedback, and don't show up until someone bids because they know that a lot of people avoid an item with that type of bidder already on-board. The shills also sometimes might have bids on other items with the same seller, and maybe a couple bid retractions. You snipe at the last second if the item is still below your pre-determined max, then no one can react. Worst thing that can happen is that another sniper or the current top bidder or even a shill has a high proxy and over-pays and drives past your max, which you should not care about anyway if it is really the max that you have already decided that you should pay before you bid. A lot of shills don't snipe to win because obviously they don't want to win and then retract since next in line will only get a "second chance" offer, rather than being stuck with max-bid if the shill has time to run you up and then retract before the end. I don't know how long it generally takes to retract a bid, but that would be interesting to know. Last second bidding also ensures that you don't talk yourself into bidding again and overpaying, or driving up "the market" if you still lose.
The only reason that I could ever come up with for bidding ahead of time is if the item is not rare but not popular either, has a low starting bid, and also a reasonable Buy It Now that is slightly higher than you think you can get it for or want to pay, but low enough that someone else might actually buy it if it sits. I'll bid the minimum, no proxy. Since a bid has been placed, the BIN goes away, and I'll throw my max bid proxy at the last second if the item is still below my max. Trick here is to remember what the BIN was and your max was or else you might end up paying more if you forget, lol. I used this strategy once and ended up losing because the auction went over my max, over the original BIN and a few dollars more to boot at the last second. Nothing you can do about that but wait for the next one to come along, which I did, and ended up paying half as much anyway.