I aggree with the 48-72 after last bid aucitons, however since the price of bitcoin changes a lot and some of those types of auctions can go on for weeks people might "cancel" their bids if there was a price spike. Maybe I will try it for an experiment here once.
Personally, I think rather than the 48-72 hours 15 minutes is fine. It's called "extended bidding." As long as you placed a big during the regular auction time, you're allowed to place bids after the auction end time. Auction only ends after 15 minutes with no bids. This is how many collectible auction houses run auctions.
It's not a good choice: the auction could end right after the first bid because most people might not even see the auction within 15 minutes.
15 minutes after the auction END TIME, not when the auction starts. So if the auction was stated to end on March 1 at 23:00 the auction is extended past that time if there has been a bid in the past 15 minutes.
This was a weird auction and its rules probably cost the owner a couple BTC. I guess the domain may not be worth the $120,000 or so 2 BTC is worth now (or is it worth that much?), but it was certainly worth 2 BTC at the time.