Find the absolutely lowest-tech chair you can.

90% of office chairs sold by places like Office Depot have buried somewhere in their description words like "For 2-4 hours of sitting per day" .. and they last about a year or two at that rate.

Even the "heavy duty" chairs are for 6-8 hours per day.

The most common point of failure (besides cheap plastic parts) is the pneumatic tube underneath, which WILL break on every office chair if you weigh more than 185 pounds.

Find a solid wood constructed upholstered (not memory foam!) chair if you can. A banker's chair like this one can have a pad added to the seat but it'll last for another 60 years just like it's already lasted that long.