The flurry of activity is due in essence to two drivers: a healthy economy and a fiercely competitive legal sector. Local area brokers say that the upshot of those drivers is the quest for top-flight space.

A high-image industry, law firms "will pay more for higher price-point buildings, and they want the best part of those buildings," says Steve Durels, executive vice president of leasing for SL Green, who brokered the Akin Gump lease. "They want the good views and the high ratio of windows--they like lots of windowed offices--and the more corners the better for partners."

The other thing they want is expansion space. "In a very competitive environment, recruiting is the lifeblood of these firms," says Lewis Miller, vice chairman of CB Richard Ellis. "It's important that they offer their space and their amenities," as part of that recruitment. There are a tremendous amount of law firms--including a lot of non-NY-based law firms coming into New York--trying to reach critical mass, which most of them view as 150 to 200 attorneys. To grow like that you need to pick up practice groups from other firms."

That means having space ready to occupy, and Miller says that as a result there is "a real requirement for fixed expansion rights and the ability to get more space over time." But everything the economy gives the economy can take away, and law firms are genetically a risk-averse sector.

"With this much growth, there also has to be planning for the downside and an exit strategy if they don't get that kind of growth," the CBRE executive, who closed the Seyfarth Shaw deal, continues. "Sublet provisions and the ability to shed space without too much interference from the building owner are becoming highly negotiated aspects of the lease."

But quantifying the value of such flexibility is an inaccurate science, the leasing executives agree. "Clearly, there's a price to be paid for every right you get in a lease," says Miller, "but you really don't parse out rent that way. There are just too many elements that go into a lease."

Nevertheless, the values are market-leaders. For example, as GlobeSt.com reported at the time, the 15-year Dechert lease alone was valued by sources at $300 million.