I'm not saying "plan locking" is not a useful feature in some cases, and maybe it would really solve this particular issue. But my experience is that when people say "I need it" in most cases it's "I've been working with X for a long time, and that's how you solve problems looking like this there." (where X is usually Oracle or DB2).

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.