Hi: There are many reasons why real estate sits on the market for a long time. It all boils down to the ratio of the following: price, exposure, location, condition, seller motivation, & incentives to the buyer's agent & to the buyer. As soon as these items are properly in sync, the property will sell. With co-ops there is 1 more level of complication, which is the co-op board. Sometimes co-ops take longer to sell because the Board has rejected buyers. If you're curious as to why a specific unit hasn't sold, I'll be happy to try & explain it. Sometimes you have to be a bit of a detective to figure it out. Please call me at 914-273-9688. Sincerely, Michael F. Levy, Principal Broker, Grand Lux Realty. www.GrandLuxRealty.com.