I think one of the main issues surrounding the concept of Oksana, Tara, and Sarah as OMGs is not necessarily the fact that they were "outa there" once they won the gold (Sarah being an exception, and I'll get back to that), it was what they had accomplished BEFORE they won. Or, more accurately, the length of time they were around at the top before they did so. Oksana blew on the scene out of literally nowhere, wins the silver at Euros, then the Worlds, then one year later she's won the gold and she's "outa there". She certainly was not the first skater to do this, as a matter of fact, it is usually considered pretty standard for skaters to "get out" once they win the OMG -- however, in Oksana's case, a year earlier, it was a case of Oksana Who? so it was like no-one really got a chance to "get to know her" so to speak because she wasn't in the top ranks of eligible skating for very long. Plus winning the gold in a controversial decision over the more established Nancy Kerrigan didn't help much either. So it's easy to dismiss Oksana as a skater who happened to have one fabulous year at just the right time as opposed to perhaps a -- I hate to use this word, but it's the only thing that comes to mind at the moment -- TRUE Olympic champion with a more established record behind her, in the vein of a Carol Heiss or a Katarina Witt (in her 2nd Olympics). Much the same can be said for Lipinski. She was fairly well known in the US by the time she'd won Worlds in '97, but internationally it was much the same -- she had one great year at just the right time, winning the Worlds and OMG; and she, too, won a controversial decision over the more established Michelle Kwan which didn't help either. Then, she, like Oksana, was "outa there". It was another case, like Oksana, of WAIT a minute, we don't even know what you're truly capable of yet. Will history remember you as one of the all-time greats (i.e, Heiss, Fleming, Hammill, Witt) or as someone who just had one fabulous year?
Sarah's case is a bit different. Remember, the Ladies free program in Salt Lake City was NOTHING to write home about. Kwan was mediocre, Slutskaya could have been much better, Cohen was concentrating so much on landing jumps that all her wonderful choreography went right out the window, and Butrskaya had a terrible competition. So this was less a case of Sarah being so terrific (although she was), it was more of a case of everyone else didn't really step up to the plate so Sarah was able to benefit. And even she realized that despite the OMG, she overall really hadn't accomplished much in her career yet, so she stuck around the extra year until school took up much of her time. And by some accounts she actually isn't finished yet, so the jury is still out.
That being said, I too would like to see the gold in Torino go to a lady with a more established top-level record than what we've seen at the last 3 Olympics. It used to be that an Olympic Gold Medal was the capoff of a good or great career, not part of the start of one that never really took off.