I work from home and spend around 8 hours per day on my computer and so my computer chair or office chair gets a lot of use.
I spend around 8 hours per day sitting in my office and computer chair so it gets worn down.
For me my office chair or computer chair lasts around 6 to 7 years before it needs replaced.
The cushion is usually what wears down faster and first but sometimes the chairs cylinder that raises and lowers the chair gives out and starts sinking within 4 years or so and sometimes if that happens I need to get a new office or computer chair.
However i had to one time use a hose clamp on the office chairs cylinder to keep it from sinking when I had no money at the time to replace the chair.
Most people do get between 5 to 7 years out of an office chair and some people replace their office or computer chairs after 10 years or so.