Filed under: Private equityIt's a good week for Sam Zell, who sold Equity Office Properties Trust (NYSE: EOP) for $39 billion. In all, he takes about $900 million. At age 65, he is certainly a veteran player of the real estate game.One of his peers, Steven Roth - who is the CEO of Vornado Realty Trust (NYSE: VNO) - is 64 years old. He dropped out of the bidding for EOP because he thought the valuation was too rich. And, today, another Old Guard real estate mogul, Mortimer Zuckerman, is taking money off the table. He is the chairman of Boston Properties Inc. (NYSE: BXP) and is 68 years old.According to an SEC filing, he is selling roughly $75 million of his stock.But, despite all of this, Blackstone's ...