When to do a vacuum for highly active table

We have a highly active table that has virtually all
entries updated every 5 minutes. Typical size of the
table is 50,000 entries, and entries have grown fat.

We are currently vaccuming hourly, and towards the end
of the hour we are seeing degradation, when compared
to the top of the hour.

Vaccum is slowly killing our system, as it is starting
to take up to 10 minutes, and load at the time of
vacuum is 6+ on a Linux box. During the vacuum,
overall system is goin unresponsive, then comes back
once vacuum completes.

If we run vacuum less frequently, degradation
continues to the point that we can't keep up with the
throughput, plus vacuum takes longer anyway.

Becoming quite a pickle:-)

We are thinking of splitting the table in two: the
part the updates often, and the part the updates
infrequently as we suspect that record size impacts
vacuum.

Any ideas?

Thanks,
Mark

-----------------