Hugh Hefner is engaged, but don't expect to see his fiancee walking down the aisle anytime soon. Sources tells Bill Zwecker that a wedding is unlikely, and that his union with 24-year-old Playmate Crystal Harris will remain a long-term Hollywood engagement. “Though in Hef’s case, how long can that be?” one source told the Sun-Times columnist in reference to the 84-year-old. But if they do marry, Harris better hope Hefner lives a long time. Zwecker hears that, like most Hollywood prenups, theirs would likely include a four-year minimum before she would see a dime.