I've always found SAN to be an effective way to bid. It's definitely not like
ebay ! This is where dealers and serious collectors come to buy.
They are just a service, it's the actual auction house that controls how the auction is run and when the realizations are posted. Some are better than others.
Many of the auction houses have live real time online bidding. You are actually able to bid against the buyers that are on site. It's fast paced and can be quite intimidating until you get accustomed to it.
Others like you say, close bids prior to the actual auction taking place. Your proxy bid is held against bidders on site or their agents. If you can't be present, it's best to make your absolute highest bid and hope for the best. Most times you will be outbid.
Onsite bidders have many advantages over internet bidders. Opportunity to inspect the lot, ability to size up the competition, no shipping charges.
Internet bidders of course save on the cost of traveling to the auction and usually sales tax but other than that they are pretty much bidding on a description and a few pictures if they are lucky.
Look on the bright side. The internet affords us a chance to participate in auctions that we never could have in the past.