When a property is listed for an eternity it normally means there is something particular to it that prevents the sale from occurring.
That something can be the price, a person can be asking too much, it could be the rights that come with the property, the status (such as a protected structure) or sometimes it can be due to unreasonable demands of different natures that sellers and buyers place on eachother.
Here is a great example of a property that hasn’t sold in a long long time, there are issues with this property in particular (in this instance I know because we had an engineer go through it).
The property has gone sale agreed with Lisney in Drumcondra and fallen through then another buyer was lined up and again the sale isn’t happenning.
The google map image shows that some time long ago Douglas Newman Good were trying to sell the property (without success one can only assume given that records don’t show any transaction having taken place).
This is why you need to know what you are doing when you view property, sometimes a place can seem like a good deal until you start tio look into it!