Now men who are not suffering from PE are also starting to buy. Much like Viagra users who don't have ED, Absorption Pharmaceuticals sees customers using Promescent merely to prolong their sexual performance. "There is a tremendous recreational component," said Abraham.
"It's definitely effective," said Scott, a 53-year-old executive who does not want his last name used. Scott heard about Promescent from a friend ("We're a bunch of old guys, so we talk about everything"), and he went online and bought a bottle. "The first time I think I oversprayed, 10 to 12 sprays," he said. The result? "My wife got annoyed, like 'Enough already!'
Since then he's adjusted his dose and says it has more than doubled his performance time. He added that, apparently, none of the Promescent transferred to his wife.
(Read more: Ads on porn sites? This business does it)
Abraham believes the PE market could become bigger than the ED market, and larger companies are starting to take notice. He said he recently turned down an offer to sell the company for about $30 million.
"I know what I have, and I know what it's worth," he said.
He plans to sell eventually, in part to help provide for Gilbert's widow and two sons. "It's kind of bittersweet," Abraham said of the company's fledgling success now that its founder is gone. "I wish he was here to see it."
—By CNBC's Jane Wells; Follow her on Twitter: