If you really need nightly vacuuming (and not just analyze), and you accidentally turn it off, you have bigger problems than planning.
This should be handled by autovacuum in modern versions, so either you're running a very old version (before 8.3 when autovacuum was enabled by default).
So either you're running a very old version (i.e. older than ~5 years - sorry, not much can be done here except for upgrading).
Or you don't have autovacuum tuned properly, or you really have strange workload. In those cases you should really talk to people on pgsql-performance.
Having been bitten two or three times by a fast query suddenly getting very slow because a heuristic in the query planner flipped over (including once in the last couple of years), I'd simply like to fix a performant enough query plan and not worry about it.
Just to make my opinion clear, pg along with linux and vim are the best pieces of software I use.