8.2 Autovacuum BUG ?

Hi,

We turned on autovacuums on 8.2 and we have a database which is read
only , it is basically a USPS database used only for address lookups
(only SELECTS, no updates/deletes/inserts).

This database has about 10gig data and yesterday autovacuum started
on this database and all of a sudden I see lot of archive logs generated
during this time, I guess it might have generated close to 3-4gig data
during this period.

It was doing only vacuum not vacuum analyze.

My question is why does it have to generate so many archive logs on
static tables ?

I am thinking these archive logs are mostly empty , the reason I am
saying that because I noticed that when I restore the db using PITR
backups for my reporting db these same logs are recovered in seconds
compared to the logs generated while vacuums are not running.

Is this a BUG ? or am I missing something here ?

Vacuum Settings
---------------------
vacuum_cost_delay = 30
vacuum_cost_limit = 150
checkpoint_segments = 64
checkpoint_timeout = 5min
checkpoint_warning = 30s
autovacuum = on
autovacuum_naptime = 120min
autovacuum_vacuum_threshold = 500
autovacuum_analyze_threshold = 250
autovacuum_vacuum_scale_factor = 0.001
autovacuum_analyze_scale_factor = 0.001
autovacuum_freeze_max_age = 200000000
autovacuum_vacuum_cost_delay = -1
autovacuum_vacuum_cost_limit = -1

Thanks!
Pallav.