These outdoor cushions are made to last. The seat cushion is a 6” thick piece of foam. The cushion will last a long time and is very supportive. The back cushion is a soft poly filling so you can really relax in these chairs. I have had Sunbrella outdoor fabric on other cushions and it is tough and long lasting. 
I bought these cushions as a replacement for 10 year old Sunbrella cushions and I expect that with care these cushions will last as long.