in January 2019, Jessica Alba, the actress and cofounder of the eco-friendly megabrand The Honest Co., threw a 40th-birthday bash for her husband, Cash Warren, producer and cofounder of lifestyle brand Pair of Thieves. Throughout his 30s, she’d organize an over-the-top pajama party every year—blowouts that would include beer pong, Twister, charades, and even a corn-hole toss. But this year, because they had recently moved into a home perched on the edge of a scenic, leafy canyon in Beverly Hills, she decided to combine the birthday with a housewarming. And after their beautiful, new, expansive backyard—a hot commodity in this part of town—had been mauled by tents, bars, and wild corn tossers at the extravaganza, she decided to retire the tradition. “He’s in his 40s now, so he can do…