The free sniping co. I have bid through will bid up to the last 10 seconds. If I was willing to pay a fee, they bid to the last 3 seconds. In other words, I could be out bid by a higher bid before the last 10 secs., or by another bidder who pays their fee and her bid would be placed just after mine.
I have won quite a few like this wheras beforehand I lost quite a lot after the last 30 secs because I couldn't get another bid in quickly enough.. The snipe company informs me if my bid has been successful, then I go ahead and pay as usual.