Great Question! It looks like you also got some great answers as well. As indicated by other realtors the days on market depends on many factors. You can use a general rule but if you need some specifics then you need to know the neighborhood, home requirements, ect. Some homes sell faster than others because of the condition they are in, the price that they offered at, and the location. A realtor can run you a specific CMA for an area and help you with defining how much time homes are selling for in a specific area..
Days on market can fluctuate greatly because of the time of the year as well. Again, a realtor can give ou specific information that would show you the best selling time in a specific area. Of course with that said there are homes that do not sell because of how they are marketed, staged, priced, and many other factors. Sounds kind of confusing doesn't it. Just like anything you have to know the statistics to come up with great information. If you need any additonal help please let me know and I will be happy to assist you..