LONDON — Kristian Haagen, 44, owns some pretty costly watches — a Patek Philippe Nautilus, an A. Lange & Sohne Datograph Perpetual, and a Patek Philippe Nautilus Chronograph. It wasn’t always so.

As a teenager growing up in Denmark, he used to sell cheap knockoffs to his friends in school. When he reached adulthood, he said, “I wanted to own a real watch.” So on a trip to Miami when he was 23, he bought three Rolexes. “Buying a Rolex was like a childhood dream come true,” he said. But why buy three? “I figured if I kept one and sold the other two, that would pay for my girlfriend’s and my trip to Miami.”

As years went by, Mr. Haagen added a Panerai to his collection. Panerai provided a crucial ingredient to his watch-buying habit. “They offered a dedicated collectors’ forum online,” he said. Mr. Haagen participated in it, as well as in a growing number of other outlets, such as Hodinkee, that offered the opportunity to engage with what he calls “other watch geeks.”

“The more you learn,” he said, “the knowledge makes you evolve into a different league.”

So, after a heart operation in 2007, “I wanted to pamper myself and celebrate coming out of the hospital alive.” He bought his first Patek Philippe. Last year, Mr. Haagen, who is now a watch specialist at Bruun Rasmussen Auctioneers, graduated to A. Lange & Sohne, which he calls “certainly the grown man’s watch brand.”