Vacuum taking an age

Hi,

I have a pretty "live" table: rows being inserted and updated more
than once 1 per second, though far, far more inserts than updates.

There are currently over 3 million rows.

It has not been vacuumed for months.

Now a vacuum on that table takes hours, and I have not let it complete
because it stays running into our daily busy time... but I've been
told its necessary because the table is slowing down.

I have begun a cron job which will do a daily analyze, and am thinking
of a weekly vacuum...
Please advise on the best way to keep this table maintained, even if
it means regularly taking the service offline early on Sunday
morning...

thanks in advance
Brian

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Brian Modra Land line: +27 23 5411 462
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6 Jan Louw Str, Prince Albert, 6930
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South Africa