Usually an expensive sofa is in use from 5 to 8 years under normal use and treatment for it. (But of course if 2,000 people sat on the couch for a year, even if it is expensive, sofa quickly loses its previous form). On average, for a family of 5 people this sofa will serve about 5 years. Then sofa’s quality will be deteriorating, although it is still possible to sit and lie on it for about eight years (if you are Lucky). But experience shows that people do not like disharmony at their home especially if you can buy something beautiful and new. Thus they go back to the store for a new sofa : )
Inexpensive sofas serve from 1 to 4 years, not more, as this type of sofas is not designed for long use. Usually, the inexpensive quality sofas are designed for occasional use, such as in a home office room or in the country house. Of course, lonely people buying a sofa do not use it in a way that it can be frayed during a year.