Shops like AUrate hope to find new customers who they can retain for the long haul. If passersby step inside and don't buy anything, at least they saw what the label has to offer. This, for a small company, is invaluable. Even if Kahn doesn't decide to come back next year, or stay permanently, she's assured some benefit.

That's a big reason pop-ups of all types are getting more popular. Such cities as New York and London host hundreds of pop-ups each year, attracting shoppers with fleeting exclusivity. A whole industry has grown around pop-up dining, where foodies can try new, one-of-a-kind culinary experiences in places ranging from the Australian outback to a farmhouse in the British countryside.

Private Events

Then there are the parties. Houses, art galleries, country clubs, and stores host celeb-packed events throughout the warmer months. It's a social scene brands can't resist. Take Armarium, a fashion rental company that will run a pop-up concierge service at a Sag Harbor hotel this summer, with stylists to help socialites figure out the right look. Armarium's name is frequently seen in social hotbeds such as New York, Los Angeles, and South Florida, seeking out shoppers attending posh events and dinner parties. For that purpose, the Hamptons aligns perfectly.

"We're servicing a girl who's looking for a statement piece," said Trisha Gregory, co-founder of Armarium. "She's not basic."

But the demographic has lured plenty of full-time tenants for the pop-ups to compete with, too. Most are established labels, not plucky startups. J. Crew, Ralph Lauren, and Club Monaco each have outposts on main shopping strips, for instance. A glimmering new Tesla showroom, now a permanent fixture in East Hampton after a successful pop-up trial last summer, was this year's biggest new opening.

Plenty of stores never come back. Joe Fresh didn't open a full-time store after operating pop-ups in multiple Hamptons towns. Neither did Rebecca Minkoff. Designer labels Milly, Isaac Mizrahi, and Tamara Mellon each opened temporarily alongside high-end boutiques but didn't stay. Dash, the Kardashian store, lasted only one season.

That doesn't necessarily mean they failed. Touting a Hamptons shop gives brands an air of exclusivity and a connection with the moneyed society. Plus, the short lives of pop-ups drum up lots of hype and exposure. For big brands, it can be worth the bet, even if the store doesn't end up profitable. For smaller labels that count every penny, there's much more hand-wringing. Even for AUrate, which has held pop-up locations before, running a shop for a full season (and paying gobs in rent) can be daunting.

"This is our riskiest one so far," said Kahn. "So yes, it's scary."

A Launching Pad