vacuum

I know that vacuum has come up in the past, and even saw the
discussion about putting a cron entry to have it run every once in a while,
but I don't remember seeing anything about having it kick off via a trigger
every so may inserts.
Is there a relative consensus for how often to run vacuum? I have a
table of about 8 columns that I fill with 100,000 items simply via a "\i
alarms.sql". After 1,000 items or so it gets extremely slow to fill with
data, and will take over a day to fill the entire thing unless I run vacuum
once a minute.
Is there a way to run vacuum every so many inserts, updates, and
deletes? (with 1 table the trigger is easy, but is there a global way to
check no matter which tables are utilized?).

Do other DBMSs such as Oracle run into the same problem and need to
be vacuumed, in their own sort of way?

Thanks for any insight,
Mike