Windsor Circle, a Durham-based retention marketing startup, is one of those early-stagers that made it look easy.

The four founders secured $350,000 in seed funding from IDEA Fund Partners and angel investors before they even built a product.

They used those funds to hire engineers to build a platform they believed could transform the way small and medium online retailers market to their most loyal customers. By the end of 2011, they already had 10 paying customers and a convertible note worth $405,000.

But then it came time to raise a Series A dollars this year, and things got tough.

“The ‘series A crunch’ idea felt like it was out there,” said Windsor CEO Matt Williamson. “There were a lot of firms at the end of their fund or raising their next one. We had a lot of great meetings but a lot people sat on their cards.”

The men plugged away, signing on more customers like Guideposts Magazine, DumDum suckers, Cricket Shirts and Moonstruck Chocolate. They began work on a powerful dashboard that would track a customer’s purchase history and prescribe the right marketing messages to get that customer purchasing more often.

Eventually, a prominent venture capital fund delivered Windsor Circle an attractive term sheet. But some terms just weren’t quite right.

“It would have allowed us to step on the gas,” Williamson said. “But ultimately, it’s important that everybody’s outcomes are shared and exciting. We just thought there were aspects of the deal that would have made that difficult.”

Existing investors ponied up in a smaller series A round, forcing smaller budgets for hiring new staff and marketing the platform.

But then something funny happened. Triangle Angel Partners offered an additional investment, and the terms were right on. Windsor Circle in November closed the $685,000 Series A round and converted the note, bringing the total to over $1 million.

“When you don’t need the money, that’s when it shows up sometimes,” Williamson said.

The beta version of the new dashboard is now live, and promises to generate a spike in sales next year, helping Windsor become cash flow positive. Already, Windsor Circle is showing big results for its existing customers. Those retailers grew their Thanksgiving to Cyber Monday sales 73 percent in 2012 over 2011. Fifty percent of that growth came from repeat buyers.

“A lot of the world looks at retail landscape through customer acquisitions, but intrinsically, all businesses know your repeat customers are your most valuable assets,” Williamson said. “We like to think of ourselves as 100 percent focused on retention marketing.”