We have lived in our house for 15 years and just bought our 3rd set of couches. So they last about 5 years but I stretch it to 7 years.
The ones in the basement that we rarely used are 15 years old... They need to be replaced but only teenage boys see them so I lack motivation to replace them.
I have always been told to spend money on the room you spend the most time so they don't wear out as fast and buy cheap ones for the rooms that don't get used as often.
Please shoot me if I have the same couch in my family room for 20 years.