On Dec. 4, as hundreds of Weil, Gotshal & Manges partners descended on Manhattan for their annual partner meeting, staff had to scramble to find space for them to meet in area hotels. All the firm’s conference rooms were booked for deal negotiations, including The Dow Chemical Co. in its proposed $130 billion all-stock merger with E.I. du Pont de Nemours & Co. and JAB Holding Co. in its proposed $13.9 billion buyout of Keurig Green Mountain Inc.

Across town at Cravath, Swaine & Moore, it was the same story. The firm’s Scott Barshay recalls one day in late fall when he juggled simultaneous telephone negotiations in four adjoining rooms that would ultimately result in four multibillion-dollar transactions. “It’s the first and, I hope, the last time that’s happened,” Barshay says.