Huge pg_toast table

I have a frequently updated table called 'audit' with 10,000 rows of about
90kb per row (90kb * 10k = 900mb).  There is a 35gb system table called
pg_toast_NNNNN where NNNNN is the oid of the 'audit' table.

My question:  should I expect a 'vacuum full' to shrink the size of this
pg_toast table?  I ask instead of just doing it because doing so would
require scheduling customer downtime since 'vacuum full' blocks access.

TIA.