If you app is serving lots of dynamic images (like mine does), and if you cache your images in FileSystem.cacheDirectory – you can not rely on the OS to clear it out for you, you have to do it yourself in the app. Or else, your app will eventually start crashing, at least on iOS (have not done much testing on Android, so don’t know how it will behave there).
Read my post about potential solution to this issue here Expo FileSystem.cacheDirectory must be cleaned manually - DEV Community 👩💻👨💻