Al Franken's seat was held up for 6 months due to court battles. That made 60 that caucus with the Democrats, counting independents Bernie Sanders and Joe Lieberman.
However, Ted Kennedy and Robert Byrd were in very poor health at the time, and rarely were able to vote. Franken was finally seated in July 2009, and Kennedy died in late August 2009, meaning the Democratic caucus had a technical supermajority for a total of 6 weeks. Except that the Senate was not in session 3 of those 6 weeks, so the supermajority lasted 3 weeks.
Of course, who knew that it actually would take 60 votes to pass ANY bill in the Senate.
That's besides the normal way of voting in the Senate.