I had a Fusion Drive on my iMac and it failed after 6 years. Instead of ripping that hard to repair beast open, I ended up switching to external storage. I first tried SD card since there was a handy slot in the back but those wear poorly too. They’re very fast on that model of iMac because of the bus connect. I ended up using a 1TB external ssd which was pretty small, cheap, and had no issues with wear. Reads and writes over USB were faster than the Fusion Drives. The main problem I had was waking up from sleep as there was as a race condition.
It was garbage technology to marry an SSD with a hard disk in this way. 2010 MBA was all SSD so should their desktops of that vintage should have been free of spinners.