Many factors can contribute to that.
The quality of the paint used is very importance.
The amount of traffic through a particular area.
Whether or not there are smokers in the home.
Is there a fireplace that is used on a regular basis during the winter months?
If you have small children?

There are many factors to consider, and each home can vary. A good quality job done by a professional crew under normal conditions should last anywhere from 4-8 years. You are more than welcome to give us a call and will be happy to evaluate your particular situation and offer you a more precise answer.