I update it the same day as Mozilla, often within a few hours.
But it takes time for the F-Droid.org repo to actually compile and eventually publish it.
I track release dates here: https://divestos.org/misc/ffa-dates.txt
You can see metadata updates here: https://gitlab.com/fdroid/fdroiddata/-/merge_requests?scope=all&state=merged&search=fennec+f-droid
Pending releases here: build - F-Droid Monitor
It should also be noted that Iceraven is not compiled from source and contains proprietary Google libraries: `com.google.android.gms:play-services-fido` ends up in the build and pulls in other parts of the Google Play Services client library · Issue #463 · fork-maintainers/iceraven-browser · GitHub