Last second bidding (call it whatever else you wish) is a good thing if you have the time and are able to be online when the auction is about to close. But some sites are keeping the auctions open if there is activity in the last few minutes, extending the bid time until the new bids stop coming for at least 5 minutes. So it depends on the site.
Unless you "have" to have it, the best thing to do is an auto-bid for the most you are willing to pay, and it keeps you from getting caught up emotionally in the competition.