How often do you run VACUUM FULL?
Normally you never have to run VACUUM (FULL). It is only necessary if the tables have become unduly bloated, either because of autovacuum being too slow or because of mass updates.

I would examine the tables you suspect to be bloated with pgstattuple to see how big free_percent is.

20% bloat is normal. Consider VACUUM (FULL) only if you have much more bloat.